Servings: 5

2 teaspoons extra virgin olive oil 2 teaspoons extra virgin olive oil
1 yellow onion peeled and diced 1 yellow onion peeled and diced
12 ounces baby bella mushrooms trimmed, scrubbed, and minced 12 ounces baby bella mushrooms trimmed, scrubbed, and minced
6 cloves garlic peeled and minced 6 cloves garlic peeled and minced
1/4 cup white wine or vermouth ¼ cup white wine or vermouth
3 tablespoons butter 3 tablespoons butter
8 ounces baby bella mushrooms trimmed, scrubbed, and sliced 8 ounces baby bella mushrooms trimmed, scrubbed, and sliced
1 teaspoon dry thyme 1 teaspoon dry thyme
3-4 tablespoons flour 3 to 4 tablespoons flour
1 cup vegetable stock plus more, if needed 1 cup vegetable stock plus more, if needed
3 cups whole milk gently warmed on stove or in microwave 3 cups whole milk gently warmed on stove or in microwave
16 ounces dry rigatoni 16 ounces dry rigatoni
Scant amount of nutmeg optional Scant amount of nutmeg optional
1/3 cup grated parmesan cheese ⅓ cup grated parmesan cheese
Salt and pepper to taste Salt and pepper to taste
Dry or fresh parsley for garnish Dry or fresh parsley for garnish

Before Starting: subheading: Before Starting:
Preheat oven to 400ºF.
Brown the Onion: subheading: Brown the Onion:
In a wide pot, heat the 2 teaspoons oil over medium heat until very hot. Add the onion and cook, stirring regularly, until well-browned and beginning to caramelize, about 15 to 20 minutes. Season lightly with salt and pepper.
Cook the Pasta: subheading: Cook the Pasta:
Bring a large pot of salted water to a boil. Cook the rigatoni about 3 to 4 minutes under al dente. Drain and set aside.
Cook the Mushrooms: subheading: Cook the Mushrooms:
Add the minced mushrooms and cook an additional 4 to 5 minutes. Season with salt and pepper. Add the garlic and cook for 45 seconds until fragrant.
Add the wine or vermouth and scrape up anything stuck to the bottom of the pot. Allow the liquid to cook off for 3 to 5 minutes. Transfer to a bowl.
Cook the Sliced Mushrooms: subheading: Cook the Sliced Mushrooms:
Heat the butter in the pot and add the sliced mushrooms. Cook until very golden brown, about 7 to 8 minutes. Season with salt, pepper, and dry thyme.
Return the minced mushrooms and onion to the pot and stir to combine.
Prepare the Roux: subheading: Prepare the Roux:
Sprinkle the flour over the mushrooms and stir to combine. Cook until aromatic, about 2 to 3 minutes being careful not to burn the flour.
Pour in the stock, whisking as you incorporate. Continue whisking until thick. Add the warm milk, one ladle at a time, whisking after each incorporation until all the milk has been added. Bring to a very low, bubbly boil and then reduce heat and simmer. Stir regularly. The sauce should be velvety and a little thick. It will thicken up more as it bakes. Taste and season to your preferences. Turn off the heat.
Prepare the Casserole: subheading: Prepare the Casserole:
Spoon a few ladles of the sauce on the bottom of the casserole and add ⅓ of the pasta. Pour a few more ladles of sauce on top of the pasta. If desired, add a scant amount of ground nutmeg on top (no more than ⅛ teaspoon). Continue on with pasta, sauce, scant nutmeg (optional) two more times until all the pasta and sauce have been used.
Sprinkle the casserole with the parmesan cheese and transfer to the preheated oven for 15 to 20 minutes or until bubbly and the cheese has melted and is turning golden brown in places. Remove from the oven and garnish with fresh or dry minced parsley.
To Serve: subheading: To Serve:
Divide the pasta between shallow bowls and garnish with more parsley, if desired. Enjoy!