The slow cooker completely eliminates the stirring part of caramelizing onions; it all goes happily unattended. Freeze the bag of soup in a bowl rather than laying it flat, so it will fit in the saucepan when it's time to thaw.
How to Make It
Place butter, thyme, and bay leaf in the bottom of a 6-quart electric slow cooker. Add onions; sprinkle with sugar. Cover and cook on HIGH for 8 hours.
Remove thyme and bay leaf; discard. Add stock, vinegar, salt, and pepper; cook, covered, on HIGH for 30 minutes.
Preheat broiler to high.
Arrange bread in a single layer on 2 baking sheets; broil 30 seconds on each side or until toasted. Place 1 cup soup in each of 12 (8-ounce) ramekins or ovenproof bowls, or follow freezing instructions. Top each serving with 2 bread slices and about 2 tablespoons cheese. Place 6 ramekins on a jelly-roll pan; broil 2 minutes or until cheese melts and begins to brown. Repeat procedure with remaining 6 ramekins, bread slices, and cheese.
Sweeter than expected,