Fill a large pot with water and bring to a boil. Add 2 Tbsps of the kosher salt and the green beans. Boil for 7 minutes, drain and set aside.

Note: I started my timer once the water returned to a boil after adding the green beans.

In the same pot over medium heat, add 2 Tbsps of the butter and once that is melted add the mushrooms, onions, and garlic. Season with kosher salt, pepper, and Old Bay seasoning. Cook for 7 minutes, stirring occasionally.

Add the heavy cream and 1/2 Tbsp of the thyme leaves. Raise the heat to high, bring to a boil, and reduce to medium low and simmer for 7 minutes. Stir in 4 oz of the grated parmesan cheese and green beans.

Let this cook a few minutes and taste for seasoning. Add more kosher salt and pepper if needed. Pour this mixture in a greased 9×13 pan.

Put the cubes of bread in a large mixing bowl. Melt the remaining 2 Tbsps butter and add to the bowl of bread crumbs along with remaining parmesan cheese and thyme leaves. Add kosher salt and pepper to taste and toss until evenly coated.

Put the bread cubes over top of the green bean and mushroom casserole. Press the bread cubes slightly into the casserole.

Place the casserole in the Traeger grill set to 400 degrees for 30 to 40 minutes.

Note: If the cream is not thickened, simply cook for a few more minutes.