If you want to start a debate with chefs, ask them to describe the perfect egg sandwich. Half of them will probably tell you that a proper version is nothing more than two eggs and American cheese on a kaiser roll-the way diners and delis have made it for decades. The rest of the chefs will likely give you a layer-by-layer description of a combo you'd never imagined. And that's where we fall. Behold, our test kitchen's ultimate egg sandwich: soft bun, runny yolk, crispy potatoes and a hit of hot sauce in the most unlikely place.
Spread the waffle fries (or other frozen potatoes) on a baking sheet and bake as the label directs. Lightly smash the fries with a spatula and push together to form a circle about the diameter of the bun; set aside on the baking sheet (keep the oven on).
Meanwhile, cook the bacon in a small nonstick skillet over medium heat, turning, until crisp, about 7 minutes. Transfer to a paper towel-lined plate to drain; break each piece in half. Wipe out the skillet.
Lay the cheese slices on the fries and return to the oven until melted, about 2 minutes. Meanwhile, melt the butter in the skillet over medium heat. Add the hot sauce and swirl to combine. Crack the egg into the skillet and cook until it starts setting, about 30 seconds. Season with salt and spoon the butter mixture over the egg white until it starts to turn orange-red, about 30 seconds. Cover and cook until the egg white is set, about 1 more minute.
Toast the bun and spread with butter. Slide the cheesy waffle fries onto the bottom bun. Top with the bacon, avocado, egg, peppers and the top bun.