1½ lbs sliced bacon, cut crosswise into 1” pieces
2 medium yellow onions, diced small
3 garlic cloves, smashed and peeled
½ c cider vinegar
½ c packed dark-brown sugar
¼ c pure maple syrup
½ c brewed coffee
¼ c bourbon
In a large skillet, cook bacon over medium-high, stirring occasionally, until fat is rendered and bacon is lightly browned, about 20 minutes (cook in batches if needed to avoid overcrowding. Take care not to overcook). With a slotted spoon, transfer bacon to paper towels to drain. Pour off all but 1 tablespoon fat from skillet (reserve for another use); add onions and garlic, and cook until onions are translucent, about 6 minutes. Add vinegar, brown sugar, maple syrup, coffee and bourbon; bring to a boil, stirring and scraping up browned bits from skillet with a wooden spoon, about 2 minutes. Add bacon and stir to combine.
Transfer mixture to a 6-quart slow cooker and cook on high, uncovered, until liquid is syrupy, 3½ to 4 hours. Transfer to a food processor; pulse until coarsely chopped. Let cool, then refrigerate in airtight containers, up to 4 weeks.