How to Make It
Bring first 4 ingredients to a boil, stirring occasionally, until sugar dissolves. Remove from heat. Discard bay leaf.
Melt butter in a large saucepan over medium heat. Stir in apple and onion; sauté 8 minutes or until onion is tender and apple begins to caramelize.
Whisk in flour, and cook, whisking constantly, 1 to 2 minutes or until smooth. Gradually add pan juices and apple juice mixture to pan, and bring to a boil. Reduce heat, and simmer, stirring occasionally, 5 minutes or until thickened. Season with salt and pepper.