Preheat your waffle iron. Begin cooking your bacon.
Whisk together the flour, baking powder, sugar and salt in a large bowl. In another bowl, whisk together the three eggs, melted butter, and milk. Make a well in the center of the dry ingredients and pour in the wet ingredients. Gently whisk them together with a few swift strokes (the batter should be lumpy). Fold in the shredded cheese.
Once your waffle iron is heated, be sure to grease it if your model needs it (I use Trader Joe's Coconut Oil Spray). Spoon 1/2 cup batter (or the amount recommended by your waffle iron's manufacturer) onto the hot iron. Spread the batter to within 1/4 inch of the edge of the grids, using a silicone or wooden spoon. Close the lid and bake until the waffle is golden brown. Keep warm in a single layer on a rack in a 200°F oven whole you finish cooking the rest.
Melt the 1-2 tbsp butter in a large skillet over medium-low heat. When hot, break 4 eggs into the skillet. Season with scant 1/8 tsp salt and a pinch of ground pepper. Cover and cook until the whites are completely set and the yolks are nearly set. Flip each egg carefully by sliding a slotted spatula under the egg, supporting the yolk, and carefully turn it over in the skillet. Cook another 30 seconds to 1-2 minutes, depending on your yolk preference (we don't do runny eggs, so we're on the 2 minute side). Repeat until all your eggs are cooked.
Place one waffle on a plate and top with your egg, bacon and avocado slices. Place another waffle on top to close your sandwich and enjoy!
Source: Waffle recipe from Joy of Cooking