In a small skillet, cook bacon over medium heat until partially cooked but not crisp. Drain on paper towels. Meanwhile, in a small saucepan, combine the coffee, brown sugar, vinegar, mustard and salt. Bring to a boil; cook and stir for 2-3 minutes or until sugar is dissolved. Stir in beans and onion.
Divide the bean mixture between two 6-oz. ramekins or custard cups coated with cooking spray. Top with bacon. Bake at 350° for 25-30 minutes or until bubbly.