Put a large pan of salted water on to boil. Scrub the potatoes and chop them into chunks around 3cm across. When the water is boiling, add the potatoes and simmer for 20 mins.
While the potatoes simmer, quarter the cherry tomatoes and pop them in a bowl. Peel and finely chop the garlic. Add it to the tomatoes. Finely shred the mint leaves and stir them into the tomatoes with 2 tbsp vinegar and ½ tbsp olive oil. Season with a pinch of salt and pepper and set aside to marinate for at least 10 mins.
Coarsely grate or shave the parmesan into thin shavings. Set to one side.
Set a griddle or frying pan over a high heat and get it smoking hot. Rub 1 tsp oil and a pinch of salt and pepper into each steak. When the pan is really hot, add the steaks and fry them for 30 secs-1 min on each side. Pop them on a warm plate and loosely cover with foil. Let them rest for up to 5 mins.
The potatoes should be tender and cooked through by now. Drain them, then tip back into the pan and add the butter. Toss in the pan to melt the butter and coat the potatoes. Season.
Pop the steaks onto 2 warm plates and top them with the cherry tomato bruschetta mix. Sprinkle over the parmesan. Serve with the potatoes and rocket on the side.