Ingredients
1 tablespoon oil
1 medium onion, sliced
1 cup Guinness
2 teaspoons grainy mustard
1 tablespoon butter, room temperature
2 slices rye, lightly toasted
1/2 cup cheddar, shredded, room temperature
2 ounces cooked corned beef, sliced or shredded, warm
Directions
Heat the oil in a pan over medium heat.
Add the onions and saute until tender, about 5-7 minutes.
Add 1/4 cup Guinness , cover and simmer until the liquid has mostly evaporated, about 15 minutes and repeat three more times.
Remove from heat and mix in grainy mustard.
Heat a non-stick pan over medium heat.
Butter the outside of each slice of bread, sprinkle half of the cheese on the inside of one slice of bread, top with half of the onions, the corned beef, the remaining onions, cheese and finally the other slice of bread.
Add the sandwich to the pan and grill until golden brown and the cheese has melted, about 2-4 minutes per side.