Begin by melting butter in a small bowl and mix in Irish whiskey. Submerge the sirloin steaks in the marinade, cover, and refrigerate for at least 3 hours.

Preheat a cast iron skillet over medium-high heat. Sear the marinated steaks for about 3-4 minutes on each side.

Transfer the skillet with steaks to a preheated oven at 350°F. Bake for approximately 10 minutes for medium doneness.

While the steak bakes, bring salted water to a boil, add chopped russet potatoes and cook until tender, about 15-20 minutes. Drain and mash with cooked kale, salt, and pepper.

In the same pan used for searing, add shallots and sauté until soft. Deglaze with Irish whiskey and stir in heavy cream, letting it simmer until thickened.

To serve, place colcannon on each plate, add the steaks on top, and drizzle with whiskey cream sauce.