Mushroom Polenta Casserole

Imagine sinking your fork into a creamy, bubbling layer of golden polenta topped with savory wild mushrooms, all enveloped in a blanket of melted cheese. This Mushroom Polenta Casserole transforms humble ingredients into a comforting masterpiece that bridges rustic Italian tradition with modern comfort food. The earthy aroma of sautéed mushrooms mingles with herbs and garlic, creating an irresistible invitation to your table. Whether you’re looking for a hearty vegetarian main dish or an impressive side, this Mushroom Polenta Casserole delivers on all fronts. You’ll learn how to create perfectly creamy polenta, prepare mushrooms that burst with flavor, and assemble a casserole that will become a family favorite.

Why You’ll Love This Recipe

This Mushroom Polenta Casserole stands out as a truly spectacular dish for numerous reasons. First, it offers an incredible textural journey – from the creamy, soft polenta base to the meaty bite of mushrooms and the crispy, golden cheese crust on top. The contrast creates a delightful eating experience that satisfies on multiple levels.

The flavor profile is equally impressive, with earthy mushrooms complemented by aromatic herbs and the subtle corn sweetness of the polenta. It’s deeply satisfying without being heavy, making it perfect for both special occasions and weeknight dinners.

What’s more, this polenta and mushroom bake requires minimal active cooking time, with most of the magic happening in the oven. The recipe is forgiving and flexible, allowing you to prep components ahead of time and assemble when ready. It’s also budget-friendly, transforming inexpensive ingredients into a dish that tastes decidedly gourmet. Even kitchen novices can achieve spectacular results with this foolproof mushroom casserole recipe.

Ingredients

For the Polenta:

• 1½ cups (255g) polenta or coarse cornmeal
• 6 cups (1.4L) vegetable broth or water
• 1 teaspoon salt
• 3 tablespoons (42g) butter
• ½ cup (50g) grated Parmesan cheese

For the Mushroom Topping:

• 1½ pounds (680g) mixed mushrooms (cremini, shiitake, oyster)
• 3 tablespoons (42g) butter
• 3 cloves garlic, minced
• 2 tablespoons fresh thyme leaves
• 1 tablespoon fresh rosemary, chopped
• ¼ cup (60ml) dry white wine
• Salt and pepper to taste
• 1 cup (100g) shredded fontina or mozzarella cheese
• ¼ cup (25g) grated Parmesan cheese for topping

The cornerstone of this recipe is the mushroom selection – a mix of varieties provides the most complex flavor. Cremini offers earthiness, shiitake contributes meatiness, and oyster mushrooms add delicate texture. The polenta should be coarse-ground for authentic texture, while good quality cheeses make a noticeable difference in the final dish.

Pro Tips

Perfect Polenta Technique: The secret to smooth, lump-free polenta is a slow introduction to liquid. Whisk the dry polenta into cold (not hot) broth in a steady stream, then bring to a gentle simmer. Stir frequently with a wooden spoon, paying special attention to the corners of the pot where lumps tend to form. Cook low and slow for at least 30 minutes—rushed polenta is grainy polenta.

Mushroom Mastery: To develop deep flavor, don’t crowd your mushrooms when sautéing. Cook them in batches if necessary, allowing each batch to gain a golden-brown sear before moving on. This caramelization is essential for developing the complex umami notes that make this Mushroom Polenta Casserole exceptional. Always dry-sauté mushrooms initially until they release their moisture before adding butter or oil.

Layering Strategy: When assembling the casserole, slightly undercook the polenta (it should be spreadable but still have some bite) since it will continue cooking in the oven. Create defined layers rather than mixing components—this creates distinct textural experiences in each bite and allows the flavors to complement rather than compete with each other.

Instructions

Step 1: Prepare the Polenta

In a large, heavy-bottomed pot, bring the vegetable broth or water and salt to a simmer. Slowly pour in the polenta in a thin stream while whisking constantly to prevent lumps. Reduce heat to low and cook, stirring frequently, for 30-40 minutes until the polenta is thick and creamy. The texture should be smooth and no longer gritty when tasted. Remove from heat and stir in the butter and Parmesan cheese until fully incorporated. The polenta should be thick but still spreadable.

Step 2: Prepare the Mushrooms

While the polenta cooks, prepare your mushrooms. Clean them gently with a damp paper towel and slice them uniformly, keeping exotic varieties in larger pieces for visual appeal. Heat a large skillet over medium-high heat. Add mushrooms in batches (without oil initially) and dry-sauté until they release their moisture, about 5 minutes. Add the butter, garlic, thyme, and rosemary. Cook until the mushrooms are golden brown and fragrant, about 5-7 more minutes. Pour in the white wine and scrape up any browned bits from the pan. Let the wine reduce almost completely, then season with salt and pepper.

Step 3: Assemble and Bake

Preheat your oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish. Spread the prepared polenta evenly across the bottom of the dish, creating a smooth layer. Distribute the mushroom mixture over the polenta, ensuring even coverage. Sprinkle the fontina or mozzarella cheese over the mushrooms, followed by the additional Parmesan. Bake uncovered for 25-30 minutes until the casserole is bubbling at the edges and the cheese has melted and turned golden brown in spots.

Step 4: Finish and Serve

Remove your Mushroom Polenta Casserole from the oven and let it rest for 5-10 minutes before serving. This resting period allows the casserole to set slightly, making it easier to portion. If desired, garnish with additional fresh herbs just before serving to add bright color and a fresh aroma. Cut into squares or scoop portions directly from the baking dish while still warm.

Variations

Protein-Packed Version: Transform this Mushroom Polenta Casserole into a more substantial main course by adding protein. Brown 8 ounces of Italian sausage (regular or plant-based) before cooking the mushrooms, then combine them for the topping. Alternatively, add 2 cups of shredded rotisserie chicken or 1½ cups of white beans to the mushroom mixture before layering it over the polenta.

Dairy-Free Adaptation: Create a completely vegan polenta mushroom bake without sacrificing creaminess. Replace butter with olive oil in both the polenta and mushroom components. For the polenta, add 2 tablespoons of nutritional yeast for cheesy flavor and substitute the Parmesan with an additional tablespoon of olive oil. Top with your favorite plant-based mozzarella-style cheese or make a quick cashew cream by blending 1 cup of soaked cashews with ¼ cup water, 1 tablespoon nutritional yeast, and a pinch of salt.

Mediterranean Twist: Give your casserole a Mediterranean flair by adding 1 cup of roasted red peppers and ½ cup of olives to the mushroom mixture. Incorporate 1 teaspoon of dried oregano and finish the baked casserole with crumbled feta cheese and fresh basil instead of additional Parmesan.

Storage and Serving

This Mushroom Polenta Casserole keeps beautifully in an airtight container in the refrigerator for up to 4 days. For best results when reheating, add a splash of broth or water before warming in a 350°F oven until heated through (about 20 minutes), which helps restore the creamy texture. Individual portions can be microwaved for 2-3 minutes, stirring halfway through.

For freezing, cool the casserole completely, then wrap tightly in foil and freeze for up to 3 months. Thaw overnight in the refrigerator before reheating as directed above.

Serve this comforting dish with a crisp green salad dressed with a simple vinaigrette to cut through the richness. For a more substantial meal, pair with roasted vegetables like asparagus or Brussels sprouts. It also makes an excellent side dish alongside a simple protein such as roasted chicken or grilled fish. For an elegant presentation, serve individual portions in shallow bowls, garnished with fresh herbs and a drizzle of high-quality olive oil.

FAQs

Can I make this polenta mushroom casserole ahead of time?
Yes! Prepare both components up to 2 days ahead and store separately in the refrigerator. The polenta will firm up, so you may need to add a splash of broth and reheat gently before assembling. Alternatively, assemble the entire casserole, cover, and refrigerate for up to 24 hours before baking. Add an extra 10-15 minutes to the baking time if cooking from cold.

Can I use quick-cooking polenta for this recipe?
While traditional polenta produces the best texture, quick-cooking polenta can be substituted in a pinch. Reduce the cooking time according to package directions, but be aware that the texture may be slightly less creamy and the flavor less developed.

My polenta always turns out lumpy. How can I prevent this?
The key is to whisk constantly while adding the polenta to the liquid in a slow, steady stream. Using cold or room temperature liquid rather than boiling also helps prevent lumps. If you do get lumps, vigorously whisk or use an immersion blender to smooth them out.

What if I can’t find exotic mushrooms?
Regular cremini or button mushrooms work perfectly fine in this recipe. To enhance their flavor, add 1 ounce of dried porcini mushrooms (rehydrated in hot water) to the mix. The soaking liquid can replace some of the wine for extra mushroom flavor.

Is this Mushroom Polenta Casserole gluten-free?
Yes, polenta is naturally gluten-free as it’s made from corn. However, always check your specific brands of broth and cheese to ensure they don’t contain gluten additives or cross-contamination if serving to someone with celiac disease or severe gluten sensitivity.

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