Heat a cast-iron skillet over medium-high heat. Rub steaks on both sides with the cut side of a garlic clove. Finely chop 1 sprig of rosemary. Season steaks with salt, pepper and rosemary, drizzle with EVOO and cook 9-10 minutes, turning once for medium-rare. Rest meat and thinly slice against grain.
Meanwhile, place shallot, arugula, basil, parsley, thyme or oregano, sage, leaves of remaining sprig of rosemary, 1 clove of garlic grated or pasted, salt, pepper, vinegar and about 1/2 cup EVOO in a food processor. Pulse into a finely chopped herb sauce. If too thick, add another tablespoon of EVOO or vinegar, you want a spoonable sauce.
Boil potatoes and parsnips until tender, drain and mash with soft herb cheese, Parmigiano, and milk or stock. Season with salt and pepper.
Serve sliced meat with mashed potatoes and sliced tomatoes alongside. Top with chimichurri.