This Cheesy Baked Chicken Has A Surprise Ingredient That Makes It Absolutely Outstanding!

6 boneless, skinless chicken breasts
1 1/2 cups sharp cheddar cheese, grated
3/4 cup whole milk
1/2 cup parmesan cheese, grated
3 tablespoons unsalted butter
2 tablespoons all-purpose flour
1 1/2 tablespoons whole grain mustard
1/2 teaspoon garlic powder
Kosher salt and freshly ground pepper, to taste
Taste and adjust seasoning, if necessary.

Preheat oven to 375ยบ F.
Season chicken breasts generously with salt and pepper and place in a large baking dish.
Cover with aluminum foil, place in oven and bake for 20 minutes.
In a large saucepan, melt butter over medium heat and whisk in flour. Cook roux for 2 minutes, stirring constantly, or until smooth, paste-like, and golden in color.
Remove pan from heat and gradually whisk in whole milk until smooth. Return to heat and bring to a boil.
Reduce heat to low and let sauce simmer for 5-7 minutes, or until thickened.
Stir in cheeses, mustard and garlic powder, and season with salt and pepper.
Remove chicken from oven and evenly pour sauce over the top.
Return to oven and bake for another 25-30 minutes, or until chicken is cooked all the way through, but still tender.
Remove from oven, serve hot and enjoy!