1. Marinate the Steaks:

1. Coat sirloin steaks in melted butter, cover, and refrigerate for at least 30 minutes for enhanced flavor.

2. Prepare the Colcannon:

2. Boil potatoes in salted water for 15-20 minutes until fork-tender.
3. In a separate pan, melt butter, add kale, and sauté for 3-4 minutes until wilted.
4. Stir in green onions and cook for another 2 minutes, then remove from heat.
5. Drain potatoes and mash them with the butter, kale, green onions, and milk until smooth.
6. Season with salt and pepper, then cover to keep warm.

3. Cook the Steaks:

7. Let steaks sit at room temperature for 15 minutes before cooking.
8. Heat a cast-iron skillet over high heat and add vegetable oil.
9. Season steaks with salt and pepper, then sear for 2-3 minutes per side until golden brown.
10. Remove steaks and let them rest while preparing the sauce.

4. Make the Cream Sauce:

11. Reduce heat to medium, melt butter, and sauté shallots and garlic for 1-2 minutes.
12. Pour in beef stock, scraping up browned bits, and simmer for 3-4 minutes.
13. Stir in heavy cream and whole grain mustard, simmering until thickened (5-7 minutes).
14. Season with salt and pepper to taste.

5. Serve:

15. Plate a scoop of colcannon, top with seared steak, and drizzle with creamy sauce.