In a large nonstick skillet, melt the 2 teaspoons butter over medium heat. Break eggs into skillet. If desired, sprinkle with salt and pepper. Reduce heat to low; cook eggs for 3 to 4 minutes or until whites are completely set and yolks just begin to harden. Gently flip eggs, being careful not to break the yolks. For over-easy eggs, cook for 30 seconds more. For over-hard eggs, cook about 1 minute more.
If desired, spread muffin bottoms with the 3 tablespoons butter. Top with cooked eggs, spinach (if desired), bacon, and cheese. Cover with muffin tops.