Healthy Breakfast Sandwich

Name: Healthy Breakfast Sandwich
Prep time: 10 min
Cook time: 20 min
Total time: 30 min
Cuisine: American
Ingredients: 6 large eggs; 4 large egg whites; 1 tablespoon olive oil; 1 small yellow onion (diced); 1 cup chopped broccoli; 1 (8 oz) package sliced mushrooms; 2 cups Spinach (roughly chopped); 2 cloves garlic (minced); 1/4 teaspoon black pepper; salt (to taste); 6 whole wheat english muffins; 6 turkey slices (optional); 6 slices cheddar cheese (optional (I used Sargento 45 calorie slices))