1. Lay the bread slices on work surface and spread with pizza sauce. Top half with 1 slice of the mozzarella, then pepperoni, pepper and mushrooms, if using. Place remaining cheese on top. Top with remaining bread slices; set aside.
2. In shallow dish, whisk together eggs, milk, cheese, oregano, salt and pepper. Dip sandwiches into egg mixture, turning to soak up the egg mixture.
3. In large non-stick skillet or griddle, melt butter over medium heat and cook sandwiches, turning once for about 4 minutes per side or until brown and crisp and cheese is melted.
Peanut Butter and Banana Variation: Omit pizza sauce, pepper, mushrooms and cheese. Substitute ½ cup (125 mL) smooth or crunchy peanut butter and 2 large bananas, thinly sliced. Omit cheese, oregano and pepper from egg mixture and use ½ tsp (2 mL) ground cinnamon. 4 minutes per side or until brown and crisp.