Cook the bacon. In a large skillet over medium heat, cook the bacon until it's crispy. Use a slotted spoon to transfer the bacon to a plate lined with paper towels. Discard all but 3 tablespoons of the bacon grease.
Sauté the aromatics. Add the shallots to the pan with the bacon grease. Sauté until the shallots are caramelized. Add the garlic and saute for 15 seconds or until fragrant.
Sweeten things up. Return the bacon to the skillet and stir in the maple syrup and apple cider vinegar. Reduce the heat to low and simmer for 15-20 minutes or until the jam has thickened to your liking.
For the burgers
Prep. While the bacon jam is simmering, preheat the grill to medium-high heat and brush the grates with olive oil.
Form the patties. Divide the beef into 4 equal portions and form each portion into a patty. Season both sides with salt and pepper.
Grill. Place the burgers on the grate, close the lid, and grill for 4 minutes (see note). Flip the burgers, close the lid, and grill for an additional 3 minutes.
Make it cheesy. Place a slice of Swiss cheese on each patty, close the lid to the grill, and grill for 1 minute or until the cheese has melted.
Let ‘em rest. Remove the burgers from the grill and allow them to rest while you toast the buns.
Toast the buns. Cut the buns in half and brush both sides of each (cut side) with butter. Place the buns on the grill, cut side down, and cook for 15 seconds or until golden brown.
Assemble the burgers. Spread mayonnaise on both sides (cut side) of each bun and place butter lettuce on the bottom half of each. Top the lettuce with a burger patty, some bacon jam, and ¼ avocado. Place the top buns on top to close the sandwiches. Serve.
Notes
Grilling the patties for 4 minutes on either side should yield medium-rare burgers. If you would like your burgers medium, grill for 5 minutes on either side. If you would like your burgers medium-well, grill for 6 minutes on either side.