Cut the steak into 1-inch pieces.
Combine all the marinade ingredients in a bowl or ziplock bag, add the meat, turn to coat, and marinate for 30 minutes, or overnight.
Set a heavy skillet over medium-high heat and add the butter.
When the foaming subsides, add the steak in batches, without crowding the pan, and leave for a minute or two to get a nice sear on the first side.
Turn and cook for a few minutes, until golden all over.
Transfer to a shallow bowl.
When all the steak is cooked, drizzle the buttery juices from the bottom of the pan over them.
Stir together the mayonnaise and garlic and serve alongside for dipping.