Step 1

Preheat the oven to 350°F/176.66°C. Prepare a 9" x 13" casserole dish with nonstick cooking spray.

Step 2

In a medium skillet over medium-high heat, melt the butter. To the butter add the mushrooms and onion. Cook for 5 to 6 minutes or until the vegetables are softened.

Step 3

Add the garlic and stir another 30 seconds to blend flavors.

Step 4

Add the flour, salt, and pepper to the skillet and stir to coat the onions and mushrooms.

Step 5

Once the flour is completely incorporated, stir in the chicken stock. Continue stirring until the mixture begins to thicken.

Step 6

Then, add half and half. Reduce the heat and stir as needed until the sauce begins to thicken and then add the Gouda cheese to the mixture.

Step 7

Continue to stir the sauce and let it continue to thicken enough to coat the back of a spoon.

Step 8

In a large bowl, mix together the chicken, green beans, and 1 cup of fried onions.

Step 9

Add the sauce and stir until everything is evenly coated.

Step 10

Transfer the mixture to the prepared casserole dish and spread evenly. Bake for 30 minutes, uncovered.

Step 11

Carefully top the casserole with the remaining fried onions and bake for 5 minutes more.

Step 12

Remove from the oven. Rest for 5 minutes and serve.