Wash and dry all produce. Preheat oven to 450 degrees. Take out 1 TBSP butter and let sit at room temperature. Peel potatoes, then trim rounded sides away to create two rectangular blocks (they should be about 9 oz each). Cut into 1/3-inch-thick sticks, like French fries. Toss on a baking sheet with a large drizzle of olive oil.

Season potatoes with salt and pepper. Bake in oven until tender and crisped, about 25 minutes, flipping halfway through. Meanwhile, finely chop parsley until you have 1 TBSP. Halve lemon and tomatoes. Mince 1 clove garlic (use the other as you like). Using a mallet or heavy-bottomed pan, finely crush peppercorns inside their bag.

In a small bowl, stir together mayonnaise, a pinch of garlic, a squeeze of lemon, and 1 tsp truffle oil (we’ll use the rest later). Season with salt, pepper, and more lemon (to taste). In another small bowl, combine parsley, butter, and a pinch of garlic. Season with salt, pepper, and more garlic (to taste). Let butter chill in fridge until ready to use.

Heat a drizzle of oil in a large pan over medium-high heat. Season steak all over with salt and crushed peppercorns (you may not use all of them). Cook in pan to desired doneness, 3-6 minutes per side. Remove from pan and set aside to rest.

Once fries are done baking, remove from oven and drizzle with 2 tsp truffle oil (you’ll have some left over). Toss to coat. Season with salt and pepper, if needed. Toss together watercress, tomatoes, a large drizzle of olive oil, and a squeeze of lemon in a medium bowl. Season with salt and pepper.

Divide steak, fries, and salad between plates. Top steak with a dollop of herbed butter. Serve with aioli on the side for dipping fries into.