Roasted Mushroom Parmesan Polenta Bake

Make it

Instructions

1. 01

   Heat the oven and prepare the mushrooms

   Position one rack in the center of the oven and heat it to 425°F. Line a rimmed baking sheet with parchment paper. Lightly grease a 9-by-13-inch baking dish with 1 tsp of 2 tbsp olive oil, reserving the remainder for cooking. Wipe and slice 680 g cremini mushrooms, then toss them on the lined sheet with 1 tbsp of the remaining oil, 1 tbsp balsamic vinegar, 1 tsp dried thyme, 1 1/2 tsp kosher salt, and 3/4 tsp black pepper. Spread the mushrooms into one even layer; roast until deeply browned at the edges and their released liquid has mostly evaporated, 18–22 minutes. | Why: Lining the sheet prevents sticking, while roasting concentrates the mushrooms' savory flavor before they are layered into the bake.

2. 02

   Cook the creamy polenta

   While the mushrooms roast, combine 4 cups water and 1 1/2 cups whole milk in a large heavy saucepan and bring to a gentle boil over medium-high heat. Whisk in 1 1/2 cups quick-cooking polenta in a slow, steady stream, then reduce the heat to low. Cook, stirring often with a wooden spoon and scraping the bottom, until the grains are tender and the polenta is thick but still loose, 18–20 minutes. If it begins to sputter, lower the heat slightly. | Why: Gradual whisking prevents lumps, and steady stirring keeps the starch from settling and scorching.

3. 03

   Make the spinach and bean layer

   Set a large skillet over medium heat and add the reserved olive oil. Peel and finely dice 1 yellow onion, then cook it with a pinch of the seasoned salt until soft and translucent, 5–6 minutes. Peel and mince 3 cloves garlic; add it and stir until fragrant, about 30 seconds. Open, rinse, and drain 15 oz cannellini beans, then fold them in and cook until hot, 2 minutes. Rinse and thoroughly dry 5 oz baby spinach if needed; add it in handfuls and toss until just wilted, 1–2 minutes. Taste and use the remaining seasoned salt and pepper as needed. | Why: Building the onion and garlic base first gives the mild beans and spinach a fuller, well-seasoned flavor.

4. 04

   Finish the polenta

   When the polenta is tender, remove the saucepan from the heat. Stir in 2 tbsp unsalted butter and 1 cup finely grated Parmesan cheese until glossy and smooth. Taste carefully and adjust with any remaining seasoned salt and pepper. The finished polenta should slowly flow from a spoon; stir in a splash of hot water if it has tightened too much. | Why: Butter and Parmesan enrich the polenta and help it stay creamy through its final bake.

5. 05

   Layer, bake, and serve

   Spoon half of the creamy polenta into the greased baking dish and level it with the back of a spoon. Spread the spinach-and-bean mixture over it, then scatter the roasted mushrooms on top. Cover with the remaining polenta and sprinkle evenly with 1 1/2 cups shredded low-moisture mozzarella cheese. Bake on the center rack until the edges bubble and the cheese is fully melted with golden spots, 10–12 minutes. Rest the bake for 5 minutes so it sets slightly, then scoop into four warm bowls and serve. | Why: Brief baking melts the topping and melds the layers, while resting makes each serving easier to spoon.