INGREDIENTS
2 media
red onions
3 Tbsps
unsalted butter
1 serving
kosher salt
1 Tbsp
red wine vinegar
2 large cloves
garlic
1/2 cup
whole milk
1/2 cup
heavy cream
1 Tbsp
grainy mustard
2 cups
gruyere cheese
1/4 cup
parmesan cheese
1 Tsp
paprika
1 serving
worcestershire sauce
1 serving
hot sauce
1 1/2 Lbs
lean ground beef
4
hamburger rolls
1 small
serrano chili