Cheesy Mushroom Casserole

Step 1

Heat the oven to 375°F and rub a 9x9 inch baking dish with 1 tbsp of the butter.

Step 2

Melt 1 tbsp butter in a large skillet over medium and cook the chopped onion until soft and golden, about 5 minutes.

Step 3

Add the 16 oz sliced mushrooms and cook until browned and their juices have evaporated, 8-10 minutes.

Step 4

Sprinkle the 2 tbsp flour over the mushrooms and stir for 1 minute until it smells toasty.

Step 5

Pour in the 1.5 cups milk, season with the 0.5 tsp salt and pepper, and simmer until the sauce coats a spoon, 3-4 minutes.

Step 6

Off the heat, stir 1.5 cups of the cheddar into the sauce until melted, then scrape it all into the baking dish.

Step 7

Top with the last 0.5 cup cheddar and the 0.75 cup breadcrumbs and bake until bubbling and golden, 20-25 minutes. Rest 5 minutes, then scatter chopped parsley or thyme over if you have it.