01 - Whisk together flour, sugar, baking powder, baking soda, and salt in a large bowl. In a separate bowl, combine milk, eggs, melted butter, and vanilla extract. Pour wet ingredients into dry and mix until just combined. Avoid overmixing to ensure tender waffles.
02 - Preheat waffle iron and lightly grease. Cook batter according to manufacturer instructions until golden and crisp. You will need 8 waffles total (4 burgers with top and bottom). Keep cooked waffles warm while preparing remaining components.
03 - Preheat oven to 400°F. Arrange bacon on foil-lined baking sheet and bake for 12-15 minutes. Remove and brush both sides with maple syrup, then return to oven for 3-4 minutes until caramelized and crispy. Cool slightly and halve each slice.
04 - Divide ground beef into 4 equal portions and form patties. Season both sides generously with salt and black pepper. Create a slight indent in the center of each patty to prevent puffing during cooking.
05 - Heat skillet or grill over medium-high heat. Cook patties for 3-4 minutes per side for medium doneness. Place cheddar slice on each patty during the final minute of cooking to melt.
06 - Whisk mayonnaise, maple syrup, Dijon mustard, and salt in small bowl until smooth and fully incorporated. Adjust seasoning to taste.
07 - Butter one side of each waffle. Toast in skillet over medium heat until golden brown and slightly crisp, about 1-2 minutes per side.
08 - Spread maple aioli on one waffle. Layer with arugula, cooked burger patty, maple bacon halves, and red onion slices. Top with second waffle and press gently. Repeat for remaining servings.
09 - Serve immediately while waffles remain crisp and burgers are warm. Cut in half if desired for easier handling.