INGREDIENTS
1 tbsp
oil
1
medium onion, sliced
1 cup
Guinness
1 tsp
Worcestershire sauce
2 tsp
grainy mustard
1 tbsp
butter, room temperature
2
slices rye, lightly toasted
1/2 cup
cheddar, shredded, room temperature
2 oz
cooked corned beef, sliced or shredded, warm