In a large skillet, cook bacon over medium heat until crisp. Remove bacon, and let drain on paper towels, reserving 1 tablespoon drippings in pan. Let bacon cool; finely chop.
Add onion and garlic to skillet; cook over medium-high heat, stirring occasionally, until lightly browned and softened, approximately 3 minutes. Add cider, vinegar, brown sugar, mustard, tomato paste, and pepper; bring to a boil. Add bacon, and reduce heat to medium-low. Simmer until liquid reduces to a glaze consistency, 3 to 4 minutes. Transfer to a heatproof bowl. Let cool completely. Cover tightly with plastic wrap, and refrigerate until needed, up to 3 days.
Recipe by TeaTime Magazine at https://teatimemagazine.com/bacon-jam-brussels-sprouts-squares/