INGREDIENTS
1 tbsp
Chives, fresh
2
Yellow onions, large
8
Eggs, large
1 tbsp
Balsamic vinegar
1 tbsp
Dijon mustard
1/4 tsp
Black pepper, freshly ground
1 1/2 tsp
Kosher salt
1 tbsp
Olive oil
2 cups
Bread, day-old
2 tbsp
Butter, unsalted
1/2 cup
Gruyere cheese
1/4 cup
Whole or 2% milk