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
Step 1: Preheat oven to 375º F.
Step 2: Season chicken breasts generously with salt and pepper and place in a large baking dish. Cover with parchament paper and then aluminum foil, place in oven and bake for 20 minutes.
Step 3: 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.
Step 4: Remove pan from heat and gradually whisk in whole milk until smooth. Return to heat and bring to a boil.
Step 5: Reduce heat to low and let sauce simmer for 5-7 minutes, or until thickened.
Step 6: Stir in cheeses, mustard and garlic powder, and season with salt and pepper. Remove chicken from oven and evenly pour sauce over the top.
Step 7: Return to oven and bake for another 25-30 minutes, or until chicken is cooked all the way through, but still tender.
Step 8: Remove from oven, serve hot.