Prep: Dice the bacon, apples and onion; mince garlic. Measure spices and liquids so everything’s within reach.
Render the bacon: Place a large, heavy skillet or Dutch oven over medium heat. Add the diced bacon in a single layer and cook, stirring occasionally, until the bacon is deeply browned and most fat is rendered (about 10–12 minutes). Remove the bacon pieces with a slotted spoon to a bowl, leaving the fat in the pan. Drain off excess fat if the pan has more than 2–3 tablespoons.
Sweat the onions: Lower heat to medium-low and add the diced onion to the reserved bacon fat (add 1 Tbsp oil only if needed). Cook slowly, stirring occasionally, until the onion is soft and beginning to caramelize — about 8–10 minutes. Add garlic in the last minute and cook until fragrant.
Add the apples: Toss the diced apples into the pan with the onions and cook 4–6 minutes until they start to soften and release juices.
Build flavor: Stir in brown sugar and maple syrup (if using), Dijon mustard, smoked paprika, cinnamon, salt, black pepper and red pepper flakes or jalapeño (if using). Mix well so the sugar begins to melt and coat the fruit and onions.
Deglaze: Turn heat to medium-high and pour in the whiskey; scrape up any browned bits from the bottom of the pan. Let the whiskey reduce by about half (1–2 minutes). Add apple cider vinegar and bring the mixture to a gentle simmer.
Simmer into jam: Return the cooked bacon to the pan. Reduce heat to low and simmer uncovered for 20–30 minutes, stirring occasionally, until the mixture has thickened and becomes glossy and spoonable. If it’s drying out before the apples are tender, add a splash of water; if too wet, increase heat slightly and reduce more.
Adjust & finish: Taste and adjust salt, acid, or sweetness—more vinegar for brightness, a pinch more brown sugar or maple for sweetness, or a touch more salt to balance. For a chunkier jam leave as is; for a smoother texture pulse briefly in a food processor or use an immersion blender, but avoid over-pureeing unless you want a spreadable puree.
Cool & store: Let the jam cool slightly, then transfer to sterilized jars or an airtight container. Refrigerate and use within the storage timeline below.