Preheat oven to 400 degrees. Lay the bacon slices out in a single layer on a foil-lined baking sheet. Bake for 14 minutes, or until the bacon is nice and crispy. Lay out on paper towels to drain and set aside, reserving 2 tablespoons of the bacon grease.

Add the bacon grease to a large skillet and heat over medium, medium low heat, then add the onions and stir around to coat with the bacon grease. Allow to slowly cook for an hour, checking every ten minutes or so to stir and scrape up any black bits that form on the bottom of the pan.

Once the onions are a dark golden brown color, deglaze the pan with the 2 tablespoons of balsamic vinegar, scraping the pan as the vinegar dissolves. Add the remaining balsamic vinegar, brown sugar, salt, and pepper and stir until a thick glaze forms, around 5 minutes.

Add the onion mixture and bacon to a food processor and pulse until the desired consistency forms. Scoop the bacon jam into a jar and devour immediately, or refrigerate until future use. Use within one week.