Prep the Ingredients:
Cut steak into 2-3″ pieces. Rub evenly with avocado oil, then season well on all sides with blackened seasoning. Let the steak sit for 10-15 minutes at room temperature while preparing the potatoes.
Peel and quarter the potatoes. Soak them in a bowl of cold water for 10 minutes to remove excess starch. Drain, then place in a pot of salted water and boil until fork-tender while cooking the steak.
Cook the Steak and Potatoes:
In a large skillet over medium-high heat, add 2-3 tablespoons of avocado oil and sear the steak pieces in the hot skillet (cook in batches to avoid overcrowding). Cook undisturbed for about 2 minutes, until a golden crust forms. Flip once and cook for an additional minute, then reduce heat to low and cook for 1 more minute. Remove the steak and set aside in a bowl.
In the same pan, add 3 tablespoons of butter and 1 tablespoon of minced garlic. Sauté until fragrant, then toss the steak bites in the garlic butter, cooking for another minute. Remove the steak and tent with foil to keep moist.
Make the Cream Sauce & Serve:
In the same pan with the residual butter and garlic, add 2 more tablespoons of butter and the remaining minced garlic. Sauté until fragrant. Slowly whisk in the heavy cream and bring to a simmer, allowing it to reduce for 3-5 minutes.
Meanwhile, drain the potatoes and mash with melted butter, warm half-and-half, cheese, garlic powder, salt, and pepper until smooth.
Into the sauce, add red pepper flakes, green onions, and Parmesan cheese. Whisk until the sauce thickens. Adjust seasoning with salt and pepper as needed.
Serve by plating the steak bites over the cheesy mashed potatoes and spooning the Parmesan cream sauce over the top.
