Step 1

Preheat oven to 375 degrees. In a 12" skillet, melt butter over medium-high heat.

Step 2

Add chicken to the pan and cook for 6 minutes. Turn chicken after 3 to 4 minutes or when it begins to brown.

Step 3

Remove chicken and place in a casserole dish. Top with the steamed asparagus. Cover and keep warm.

Step 4

Add onions and mushrooms to the skillet. Sautee until tender.

Step 5

Reduce heat to medium and add chicken broth, cream, salt, pepper, thyme, dijon, mayonnaise, and lemon juice.

Step 6

Whisk together and bring to a simmer. Cook until sauce is reduced and starts to thicken about 8 to 10 minutes. Stir frequently. (Optional) stir in xanthan gum to further thicken sauce if needed, stir.

Step 7

Pour the mixture over the casserole. Stir in cheese.

Step 8

Sprinkle the top with the remaining cheeses. Bake for 30 minutes until bubbly and chicken is done.