In large skillet, cook bacon over medium heat, stirring often, until crisp, 10 to 15 minutes. Reserving¼ cups fat from pan and straining through fine-mesh sieve, drain.

Return reserved fat to pan; cook onion over medium heat, stirring often, until softened and deep brown, 6 to 8 minutes. Add jalapeño peppers, garlic and salt; cook, stirring often, until jalapeño peppers are softened, about 4 minutes. Scrape onion mixture into saucepan. Add bacon, maple syrup, vinegar, pepper and¼ cups water; bring to boil. Reduce heat to medium and simmer, stirring often, until mixture is thickened and reaches jam-like consistency, about 10 minutes. Let cool completely.

Pack into sterilized 2-cup canning jar; seal tightly. (Make-ahead: Refrigerate for up to 1 month; let stand at room temperature for 30 minutes before serving.)