Line bottom of a 13 x 9 x 2 buttered baking dish with bread. Top with chopped chicken.
In a small frying pan, melt 2 Tbsp. of butter over medium heat. Add mushrooms and sauté until browned, 3 to 5 minutes. Remove from heat and add to baking dish.
Top with cheese and tomatoes. In a large bowl, combine milk, eggs, salt and pepper. Mix until well blended. Pour over chicken.
Bake at 350 degrees for 50 minutes.