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 for 15–18 minutes until fork-tender.
02 - Drain potatoes thoroughly, add butter, warmed milk, heavy cream, salt, and pepper, then mash until smooth and creamy. Cover and keep warm.
03 - Pat steak cubes dry with paper towels, then season evenly with salt and black pepper.
04 - Heat olive oil in a large skillet over high heat, add steak cubes in a single layer and sear 1–2 minutes per side until browned but still juicy. Remove and set aside.
05 - Lower heat to medium, add 2 tbsp butter to the skillet, once melted add minced garlic and sauté for 30 seconds until fragrant.
06 - Return steak bites to skillet, add remaining 2 tbsp butter, toss to coat in garlic butter, cook an additional 1 minute, then remove from heat and sprinkle with chopped parsley.
07 - Serve steak bites over mashed potatoes and spoon extra garlic butter from the skillet over the top.