Place whole red potatoes (or cut into chunks if potatoes are large) in a Saucier. Cover with cold water and turn the heat to medium-high. Bring the water to a boil, add a large pinch of salt, and lower heat to maintain a simmer.

Cook potatoes until fork-tender, about 12-15 minutes, then immediately drain and set aside on a paper towel-lined plate.

While the potatoes are cooking, temper the steak by bringing it to room temperature, at least 10 minutes. Blot dry and season on both sides with salt and pepper.

Place a Stainless Clad Frying Pan over medium-high until hot, 1-2 minutes. Drizzle with 1 Tbsp. oil, then cook steak to medium rare, about 2-3 minutes per side depending on its thickness (a cake tester should come out just warm).

Let the steak rest for 5-6 minutes, in a warm location (like on top of the stove) and reserve the pan.

While the steak is resting, smash down the cooled potatoes on the plate. Place a second Stainless Clad Frying Pan over medium-high until hot. Drizzle with remaining 1 Tbsp. oil, and add potatoes and garlic.

When one side of potatoes are golden brown, carefully flip over, and cook until crispy, 2-3 minutes more. Add the chopped rosemary, and carefully toss for another 30 seconds. Drain on a paper towel-lined plate.

Place reserved steak pan over medium heat. Add 1 Tbsp. butter and sweat shallots and thyme for 30 seconds, stirring frequently, scraping up fond from the bottom of the pan.

Add ½ tsp. black pepper and cook for 10 seconds, then deglaze with brandy or red wine, reducing the heat slightly. Let the alcohol cook off completely, then add beef stock. Allow the mixture to reduce by about half.

Once reduced, add heavy cream and green peppercorns with brine, letting the sauce cook for 1-2 minutes more. You should be able to drag your spatula through the sauce and leave a trail behind.

Reduce the heat to low, and add the remaining 1 Tbsp. butter, letting it melt. Your sauce should be thick enough to coat the back of a spoon.

Once desired consistency has been achieved, add the sherry vinegar. Taste and adjust seasoning as needed.

To serve, slice the steak against the grain, top with finishing salt, and plate with potatoes, drizzling green peppercorn sauce over top.