INGREDIENTS
1
Bay leaf
5
lbs Sweet onions, large
6
Thyme, sprigs
6 cups
Beef stock, unsalted
1 tsp
Black pepper
1 1/2 tsp
Kosher salt
1 tbsp
Sugar
2 tbsp
Red wine vinegar
1
24 (1/2-ounce) slices French bread baguette, whole-grain
1/4 cup
Butter, unsalted
5 oz
Gruyere cheese