Corned Beef Panini with Caramelized Guinness Onions

sliced marble rye

Dijon mustard

(or to taste) prepared horseradish sauce

sweet onions, sliced thinly

Guinness draught beer

Worcestershire sauce

salt and pepper, to your liking

thin slices of cheddar cheese

thin slices of leftover Certified Angus Beef®  corned beef, cooked

butter