In a mixing bowl, combine melted butter with Irish whiskey. Submerge sirloin steak and marinate for at least 3 hours in the refrigerator.

Preheat a cast iron skillet over medium-high heat for about 5 minutes. Sear marinated steak for 3-4 minutes on each side until a brown crust forms.

Transfer the seared steak to a preheated oven at 350°F. Bake for about 10 minutes, or until it reaches desired doneness.

Peel and boil potatoes in salted water until tender, about 15-20 minutes. Mash and mix with cooked kale, seasoning to taste.

In the same skillet, sauté chopped shallots until translucent, deglaze with whiskey, and then stir in cream, simmering until thickened.

Plate the steak over colcannon, drizzle with whiskey cream sauce, and serve.