Lay the bacon slices in a single layer in a large skillet. Fry over medium heat until it begins to get tinged with brown. Fry on both sides. Remove from pan, but save grease.
Melt butter in skillet. Crack eggs into pan, being careful not to break yolks. Place tomato slices, mushrooms, and bread in pan. Fry gently, stirring mushrooms and tomatoes occasionally. Keep everything separate. Turn bread over to brown on both sides.
When egg whites are set, but yolks are still runny, dish half of everything onto each of 2 warmed plates, and serve immediately.