Boil the potatoes in salted water for 15-18 minutes until very tender, then drain well.
Mash the potatoes with the dairy free butter, warm almond milk and salt until smooth and fluffy. Cover and keep warm.
Pat the steak cubes very dry with paper towels and season all over with the salt and black pepper. Dry steak is the key to a deep golden crust.
Heat the olive oil in a large skillet over high heat until shimmering. Sear the steak bites in a single layer for 2-3 minutes, turning once, until browned outside and medium inside. Work in two batches so the pan stays hot.
Return all the steak to the skillet, lower the heat to medium, and add the dairy free butter and garlic. Toss for 1 minute until the garlic is fragrant and every bite is glossy.
Sprinkle the steak with fresh parsley.
Spoon the mashed potatoes onto plates, pile the garlic butter steak bites on top, and drizzle any pan juices over everything before serving.