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—do not overmix.
02 - Preheat waffle iron and lightly grease. Cook waffles according to manufacturer's instructions until golden and crisp. You'll need 8 waffles total (4 burgers, top and bottom). Set aside and keep warm.
03 - Preheat oven to 400°F. Arrange bacon on a foil-lined baking sheet. Bake for 12–15 minutes, then brush both sides with maple syrup. Return to oven for 3–4 minutes until caramelized and crispy. Cool slightly and halve slices.
04 - Divide ground beef into 4 equal portions and form into patties. Season both sides generously with salt and pepper.
05 - Heat skillet or grill over medium-high heat. Cook burgers 3–4 minutes per side for medium doneness. Place a cheddar slice on each patty during the final minute to melt.
06 - Whisk together mayonnaise, maple syrup, Dijon mustard, and a pinch of salt in a small bowl until smooth and combined.
07 - Butter one side of each waffle and toast in a skillet over medium heat until golden brown and crispy.
08 - Spread maple aioli on one waffle. Layer with arugula, burger patty, maple bacon, and red onion slices. Top with a second waffle. Repeat for remaining servings.
09 - Serve immediately while warm and crispy.