INGREDIENTS
4 tbsp
canola oil
4 cups
onion
1 1/2 tsp
kosher salt
1 1/4 lb
ground chuck
1/2 tsp
pepper
1/4 cup
mayonnaise
1 tbsp
dijon mustard
1 tbsp
barbecue sauce
1 tbsp
ketchup
3/4 cup
sharp cheddar cheese
8 slices
sourdough bread
4 slices
swiss cheese
4 tbsp
butter