Boil potatoes in salted water until tender, about 15-20 minutes.
Season steaks generously with salt and pepper.
Sear steaks in hot oil in a cast-iron skillet 3-4 minutes per side; rest.
Sauté mushrooms in butter in the same pan until golden.
Add garlic, then pour in broth and cream; simmer until thickened.
Mash drained potatoes with butter and milk until smooth.
Slice rested steak against the grain.
Plate mash, top with steak, and spoon over creamy mushroom sauce.
Tip: Rest the steak at least 5 minutes before slicing for juicier results.
Tip: Scrape up the browned bits in the pan for maximum flavor in the sauce.