Place mince into a bowl, season with a pinch of salt and pepper, and use your hands to mix well.
Shape the mince into four patties and chill for 10 minutes.
Heat frying pan over a high heat and toast burger buns for about a minute.
When toasted, place buns to one side.
Add the oil to the pan, followed by the burgers.
Cook burgers for 3-5 minutes either side, until juices run clear.
While the burgers are cooking, dissolve the stock cube in the 100ml boiling water.
Mix the mustard and Worcestershire sauce into the beef stock.
Place the burgers on a plate and top with the NI cheese before wrapping well with foil to keep warm.
Add the whiskey to the pan, stirring well to deglaze the beef juices (this is what makes it taste really good).
Stir in the beef stock mixture, followed by the NI double cream.
Simmer until thickened, about 2-4 minutes. Add a little water if it is too thick.
Place the NI cheddar topped burgers into the buns, topping with the peppercorn sauce and rocket.