Pat elk dry and saute in the butter over medium heat until it’s browned, about 3 minutes on each side for medium rare 

Remove from pan and set aside, cover with foil

Add the onion to the pan and cook for a minute or so

Add garlic and cook for another minute

Deglaze pan with whiskey, scraping the bottom of the pan to get all the good bits

Let the alcohol cook out of the sauce for a few minutes

Whisk in beef stock, tomato paste, Worcestershire and mustard

Let it simmer over medium heat for 4 minutes or until reduced to a glaze

Turn off the heat and let sit for a minute

Add cream, stir to combine 

Serve with the steak 

Garnish with basil