Hot Chicken Sandwich Casserole 4 large chicken breasts, cooked and diced 3 boiled eggs, chopped 1 small jar mushrooms 1/2 cup mayonnaise 1 small onion, diced 16 slices thin white bread 1 can cream of chicken soup 1 (8 ounce) container sour cream Butter bread on both sides and cut off crusts. Place 8 slices in rectangular baking dish, side by side. Mix together remaining ingredients and spread over bread slices. Top with other 8 slices of bread. Mix together cream of chicken soup and sour cream. Spread over top layer of bread. Refrigerate overnight. Bake in preheated oven at 300 degrees F for 1 hour. Set oven to 350 degrees F for 5 minutes to brown top lightly. Cut into squares to serve.