INGREDIENTS:

2 1/2 lbs chicken breasts (4 to 5 large), cut into 1 -inch thick strips
1 1/2 tsp sea salt plus more to taste
1/4 tsp black pepper plus more to taste
1 cup all-purpose flour to coat the chicken
6 Tbsp olive oil divided
1 pound white mushrooms thickly sliced
1 medium onion finely diced

INGREDIENTS FOR THE SAUCE:

3 Tbsp unsalted butter
3 Tbsp all-purpose flour for the sauce
1 1/2 cups chicken broth
1 Tbsp lemon juice
1 cup half and half or 1/2 cup milk + 1/2 cup heavy cream

How to Make the Best Chicken Mushroom Casserole:

1.  Season chicken with salt and pepper and dredge both sides in flour. Heat 3 Tbsp oil in a large skillet over medium/high heat. Once oil is hot, add chicken and saute until golden. Work in batches if needed so you don’t crowd your pan. Don’t worry about cooking the chicken through; it still needs to go in the oven. Transfer chicken to a 13×9 casserole baking dish.

2. Scrape of any debris from the skillet. Add 3 Tbsp oil along with sliced mushrooms and diced onions and saute until soft and golden. Add garlic and saute another 1-2 min. Spread mixture over the chicken.

3. In a medium saucepan (or in the same pan you’ve been using), melt 3 Tbsp butter. Whisk in 3 Tbsp flour until lightly golden (1-2 min).

4. Add 1 1/2 cups chicken broth, 1 Tbsp lemon juice, 1/4 tsp pepper, and whisk until smooth. Add 1 cup half and half and bring to a simmer. Season with salt and pepper to taste

5. Pour sauce over the chicken casserole. Cover with foil and bake chicken and mushroom casserole at 350F for 45 minutes. Serve warm or hot over mashed potatoes, pasta or rice.

Can Chicken Casserole Be Frozen?

Yes! You can freeze leftovers. One of my readers shared her method: It works! I took the pan out of the freezer, left it in the fridge most of the day and reheated it in a 350 degree oven for about 40 minutes.