Begin by melting butter in a microwave-safe bowl and mixing in a generous splash of Irish whiskey. Place your sirloin steak in a resealable plastic bag, pour the whiskey mixture over it, and seal tightly. Allow the steak to marinate in the refrigerator for at least 3 hours, or overnight if you want deeper flavor penetration.

Once marinated, heat a cast iron skillet over medium-high heat until it’s hot. Remove the steak from the marinade, allowing excess liquid to drip off, and place it in the skillet. Sear the steak for about 3-4 minutes on each side until it develops a beautifully browned crust.

Preheat your oven to 350°F (175°C). Once the steak is seared, transfer it to a baking dish and place it in the oven. Bake for approximately 10 minutes, depending on your desired level of doneness.

While the steak is baking, bring a large pot of salted water to a boil and add peeled Russet potatoes. Boil the potatoes until fork-tender, about 15-20 minutes. In a separate pan, lightly sauté chopped kale until wilted. Once the potatoes are tender, drain them, mash them until smooth, and mix in the sautéed kale along with salt and pepper to taste.

In the same skillet used for searing the steak, add finely chopped shallots over medium heat and sauté until they're soft and translucent. Deglaze the pan with the whiskey from the marinade, letting it simmer for 1-2 minutes. Stir in heavy cream and simmer for an additional 5 minutes.

Remove the steak from the oven and let it rest for 5 minutes. Plate a generous scoop of creamy colcannon and place the steak on top. Drizzle the whiskey cream sauce over the steak before serving.