Cook the bacon until it is cooked through but still slightly flexible. Avoid cooking it until very crisp since it will cook again in the waffle maker. Transfer the bacon to a paper towel-lined plate and blot well to remove excess grease. Let it cool slightly.
In a medium bowl, whisk together the flour, baking powder, and salt.
In a separate large bowl, whisk together the egg, milk, maple syrup, oil, vanilla extract, and melted, slightly cooled butter until well combined.
Add the dry ingredients to the wet ingredients and mix until just combined. Do not overmix. Let the waffle batter rest for 5 minutes as you preheat the waffle maker. After 5 minutes, give the batter a very gentle stir. After resting, the batter should be thick but still easily dippable. If it seems too thick to evenly coat the bacon, add milk 1 tablespoon at a time until it reaches the right consistency.
Fold one strip of cooked bacon in half, then dip it into the waffle batter, making sure it is fully coated on all sides. Lift the coated bacon out of the batter and allow any excess to drip off for a few seconds. Folding the bacon gives you more bacon flavor in each bite, but you can also leave the strips whole and dip them individually if you prefer a lighter bacon flavor.
Place the coated bacon strip onto the preheated waffle maker. Depending on the size of your strips and the size of your waffle maker, you may be able to fit two or more slices in at a time. Close the waffle maker, press down gently, and cook for about 3.5 to 4 minutes, or until the waffle coating is golden and cooked through. Repeat with the remaining bacon strips.
Serve the bacon waffles warm with maple syrup on the side for dipping. For even more maple flavor, combine 1 tablespoon melted butter with 1 tablespoon maple syrup and lightly brush the mixture over the warm bacon waffles before serving.