Trim fat from meat. If necessary, cut meat to fit into a 3 1/2- or 4-quart slow cooker. In cooker, combine onions and bay leaf; add meat. In a medium bowl, combine beer, chili sauce, brown sugar, garlic, thyme, salt and pepper. Pour over meat.
Cover and cook on low-heat setting for 10 to 12 hours or high-heat setting for 5 to 6 hours.
Using a slotted spoon, transfer meat and onion to a serving platter. Slice meat across the grain; cover and keep warm. Discard bay leaf.
For sauce, pour enough of the cooking liquid into a 4-cup glass measuring cup to equal 2 1/2 cups; skim off fat. Discard the remaining cooking liquid. In a medium saucepan, combine cornstarch and the cold water; stir in the 2 1/2 cups cooking liquid. Cook and stir over medium heat until thickened and bubbly. Cook and stir for 2 minutes more. Serve meat and onions with sauce.
Tip: We do not recommend using a sugar substitute for this recipe.
2 1/2 lean protein, 1/2 fat, 1/2 starch, 1/2 vegetable