Creamed Chicken-n-Biscuits

Creamed Chicken-n-Biscuits
1 small onion
1 1/2 teaspoons butter
2 lbs chopped cooked chicken breasts or boneless skinless chicken thighs
1 (10 3/4 ounce) can cream of chicken soup
1/2 cup mayonnaise
1 cup milk
1/2 cup chopped pimiento or sauteed red bell pepper or jarred roasted red pepper
1 1/2 cups shredded mild cheddar cheese
refrigerated biscuits (or homemade biscuits)
Preheat oven to 350. Grease the bottom and sides of an 11x7 inch baking dish or 10 inch quiche dish. Chop the onion. Heat butter in a small nonstick skillet and saute until tender. Combine cooked onion, soup, chicken, milk, pimiento, and mayo in a bowl and then turn into the prepared baking dish. Bake for 15 minutes and remove from oven. Sprinkle 1 cup of the cheese over the baked mixture. Arrange biscuits decoratively in a single layer and sprinkle remaining 1/2 cup cheese over them. Return casserole to oven and bake until biscuits are golden brown and sauce is bubbly, usually about 20 minutes longer.