1 cup chopped mushrooms (I used a mix of button, baby bella, shiitake, and hen of the wood, but use any combination you like here)
1/2 small onion, minced, about 1/2 cup
1 clove garlic, minced
1/4 cup frozen chopped spinach, thawed and drained well
1/4 teaspoon crushed red pepper
1/8 teaspoon dry thyme
1/4 cup all-purpose flour
1 cup half and half
1 cup chicken stock
1/4 teaspoon dry mustard powder
4 ounces mild cheddar cheese, shredded
4 ounces Monterey Jack cheese, shredded
1/2 teaspoon kosher salt
1/2 teaspoon fresh cracked black pepper
1/4 cup fresh grated Parmesan cheese, plus more for garnish
Heat a large non-stick skillet over medium heat.
Lightly spray the pan with non-stick cooking spray and add 1/3 of the squash. Cook, stirring frequently, until the squash has browned slightly, and the squash has dried out some, about 4 minutes. Transfer the squash to a bowl and repeat with the remaining squash. Set the squash aside.
Heat the oven to 375 F and spray 1 1 1/2-quart casserole dish, or 4 8-ounce ramekins, with non-stick cooking spray.
In a medium pot over medium heat add the butter. Once the butter melts and starts to foam add the mushrooms and onions. Cook, stirring often, until the onions soften, about 5 minutes. Add the spinach, garlic, red pepper, and thyme and cook until the garlic and spices are fragrant, about 1 minute.
Sprinkle the flour over the vegetable mixture and stir to combine. Cook, stirring constantly, until the flour just begins to brown, about 5 minutes, then slowly whisk in the half and half and chicken stock. Add the dry mustard powder and whisk well. Bring the mixture to a boil, whisking constantly, then reduce the heat to medium low and cook for 3 minutes, or until the sauce is thick enough to thickly coat the back of a spoon.
Turn off the heat and add the shredded cheddar and Monterey Jack cheese in three additions, making sure the cheese is completely melted before adding the next addition. Stir in the squash and season with salt and pepper.
Transfer the mixture to the prepared casserole dish and bake for 25 minutes. After 25 minutes sprinkle the shredded Parmesan cheese overt he casserole and return to the oven for 20 to 25 minutes more, or until the cheese is browned and the casserole is bubbling vigorously throughout. Remove from the oven and cool for 10 minutes before serving.
Recipe by Baking and Cooking Blog - Evil Shenanigans at http://www.evilshenanigans.com/2013/04/cheesy-baked-spaghetti-squash/