Method
Slicing: Slice the mushrooms and onions into uniform strips.
Sautéing Vegetables: Heat a mixture of oil and butter in a heavy-bottomed skillet over medium heat. Add the sliced mushrooms and onions, seasoning with a pinch of salt and pepper. Sauté until the vegetables develop a golden brown color, approximately 7 to 10 minutes. Stir occasionally to ensure even cooking. Remove the sautéed vegetables from the skillet and set them aside.
Searing Steak: Increase the heat to high. Add the steak strips to the skillet in a single layer, ensuring there is sufficient space for browning. Sear the steak for 3 to 5 minutes, seasoning with additional salt and pepper. The steak should achieve a rich brown crust without steaming.
Deglazing: Deglaze the hot skillet with a splash of cider vinegar, allowing it to cook off. Scrape the bottom of the skillet with a wooden spoon to release any browned bits, which will enhance the flavor of the sauce.
Building Sauce: Add the beef stock, mustard, and bay leaf to the skillet. Stir to combine. Return the sautéed mushrooms and onions to the skillet. Let the mixture simmer for an additional 3 minutes until all components are thoroughly heated.
Finishing Sauce: Stir in the full-fat sour cream until the sauce is smooth and creamy. Adjust seasoning with additional salt and pepper to taste.
Garnish: Garnish with freshly chopped parsley or dill
Serving with ideas: Cauliflower Rice, Keto-Friendly, Mashed Cauliflower, Keto-Friendly, Zoodles, Keto-Friendly, Vegetable Pasta, Keto-Friendly, Roasted Vegetables, Keto-Friendly, Zucchini Fritters, Keto-Friendly or Green Salad, Keto-Friendly.
Refrigerating: Store leftovers in an airtight container in the fridge for up to 3 days. Reheat gently over medium-low heat. Add a splash of beef broth or water if the sauce is too thick.
Freezing: Freeze in an airtight, freezer-safe container for up to 2 months. For best texture, freeze the beef and sauce separately if possible. Defrost overnight in the refrigerator and reheat on the stove over low heat, stirring occasionally.