Use a mild-flavored beer (such as a pilsner) for the best results; heavier beers, such as stout or porter, will make the sauce bitter.
Heat olive oil in a large saucepan over medium heat. Add onion; cook 5 minutes or until tender, stirring occasionally. Add peaches, black pepper, salt, and garlic; cook 1 minute, stirring frequently. Stir in beer and remaining ingredients, and bring to a boil. Reduce heat, and simmer, uncovered, 30 minutes. Place half of mixture in a blender. Remove center piece of blender lid (to allow steam to escape); secure lid on blender. Place a clean dish towel over opening in blender lid (to prevent spills). Process until smooth. Pour pureed mixture into a medium bowl. Repeat procedure with remaining mixture.
Note: Refrigerate sauce in an airtight container for up to 10 days.
Made this for the 2nd time this weekend and it really did disappoint. Not crazy about the flavors, or lack of, at all. Will try to doctor it up if I try it again.