Pat steak cubes dry with paper towels and season thoroughly with salt and pepper.
Heat olive oil in a large cast-iron skillet over high heat until just smoking.
Add steak cubes in a single layer, searing for 2 minutes per side until a crust forms and internal temperature reaches desired level of doneness.
Reduce heat to medium, add 2 tablespoons of butter and half of the minced garlic to the pan, tossing the steak to coat for 1 minute.
Remove steak from the pan and set aside on a plate.
In the same skillet over medium heat, add the remaining butter and garlic, cooking for 30 seconds until fragrant.
Whisk in the heavy cream and garlic powder, scraping the bottom of the pan to release browned bits (fond).
Simmer the cream for 2-3 minutes until slightly thickened, then stir in the Parmesan cheese until melted and smooth.
Return the steak bites to the pan, tossing to coat in the sauce, and garnish with chopped parsley before serving.