01 - Place potatoes in a large pot, cover with cold water, add a pinch of salt, bring to a boil, then reduce heat and simmer 15–18 minutes until fork-tender.
02 - Drain potatoes well. Add butter, warmed milk, heavy cream, salt, and pepper. Mash until smooth and creamy. Cover and keep warm.
03 - Pat steak cubes dry with paper towels. Season evenly with salt and black pepper.
04 - Heat olive oil over high heat in a large skillet. Add steak cubes in a single layer, searing 1–2 minutes per side until browned yet juicy. Remove and set aside.
05 - Reduce heat to medium. Add 2 tbsp butter to skillet. Once melted, sauté minced garlic for 30 seconds until fragrant.
06 - Return steak bites to skillet, add remaining 2 tbsp butter, and toss to coat thoroughly with garlic butter. Cook 1 additional minute. Remove from heat and sprinkle with chopped parsley.
07 - Plate steak bites atop creamy mashed potatoes. Spoon additional garlic butter from skillet over the top before serving.