Warm up your soul with this casserole!

- 2 1/2 pounds red potatoes
- 8 ounces fresh mushrooms
- 1/2 diced onion
- 3 cloves garlic
- 3 tablespoons butter
- 1 teaspoon salt
- 1 teaspoon black pepper
- 1 teaspoon fresh thyme
- 1 1/2 tablespoon flour
- 1 1/2 cup milk
- 1 1/2 cup heavy cream
- 7 ounces Gouda