Transport yourself to an intimate French bistro with this classic meal of peppercorn-crusted sirloin served with a creamy peppercorn sauce. Baked cheesy cauliflower gratin accompanies this dish that's sure to become a favorite.
Remove leaves from cauliflower head, core, and coarsely chop. Trim ends off green beans. Mince chives. Pat steaks dry, and season both sides with ¼ tsp. salt. Sprinkle half the cracked peppercorns (reserve remaining for sauce) on one side of each steak, pressing gently to adhere.
Make the Cauliflower Gratin
Add cauliflower to boiling water. Cook until tender, 5-7 minutes. Drain in a colander and return to pot. Add ⅓ the butter and 2 Tbsp. evaporated milk and mash until desired consistency is reached. Stir in ⅓ the cheese and season with ½ tsp. salt and ¼ tsp. pepper. Transfer cauliflower to prepared casserole dish, sprinkle with remaining cheese, and place dish on prepared baking sheet. Bake until golden brown, 12-15 minutes. While cauliflower gratin bakes, cook steak.
Cook the Steak
Place a medium non-stick pan over medium-high heat and add 1 tsp. olive oil. Add steaks, peppercorn side down, pressing firmly into place. Reduce heat to medium, add ⅓ the remaining butter (reserve remaining for sauce), and cook undisturbed until browned, 4 minutes. Flip, and cook until steaks reach a minimum internal temperature of 145 degrees, 3-5 minutes. Transfer steaks to a plate and rest 5 minutes. Reserve pan; no need to wipe clean.
Make the Sauce
Return pan used to cook steaks to high heat. Add remaining peppercorns and toast 30 seconds. Add sherry, bring to a boil, and cook 1 minute. Add remaining evaporated milk and demi-glace, return to a boil, and cook 2 minutes. Remove from burner and stir in remaining butter. Transfer sauce to a bowl, rinse pan clean, and reserve.
Make the Green Beans and Sour Cream
Return pan used to make sauce to high heat. Add ½ tsp. olive oil, green beans, ¼ cup water, and a pinch of salt and pepper to hot pan. Cover and cook until green beans are bright green and slightly tender, 3-4 minutes. In a small mixing bowl, combine sour cream with chives.
Plate the Dish
Place a serving of green beans and a scoop of mashed cauliflower on a plate. Add a dollop of chive sour cream atop cauliflower. Add sauce to plate and prop steak au poivre up against green beans.