Preheat your oven to 425°F (220°C).

In a large bowl, toss the thinly cut potatoes with olive oil, sea salt, and chopped rosemary until evenly coated.

Spread the potatoes in a single layer on a baking sheet lined with parchment paper.

Bake in the preheated oven for 25-30 minutes, flipping halfway through, until they are golden and crispy.

While the fries are baking, preheat a cast-iron skillet over medium-high heat.

Season the filet mignon steaks generously with salt and freshly ground black pepper.

Once the skillet is hot, add the steaks and sear for about 4-5 minutes on each side for medium-rare, or until they reach your desired doneness.

During the last minute of cooking, add truffle butter to the skillet and spoon the melted butter over the steaks.

Remove the steaks from the skillet and let them rest for about 5 minutes. Garnish with fresh rosemary sprigs.

In the same skillet used for the steaks, add olive oil and sauté the shallots over medium heat until softened, about 2-3 minutes.

Pour in the beef broth and scrape the bottom of the skillet to deglaze, bringing the mixture to a simmer.

Stir in the heavy cream and crushed black peppercorns, allowing the sauce to thicken slightly, about 3-5 minutes. Season with salt to taste.

Plate the filet mignon alongside a generous serving of rosemary-salted shoestring fries. Drizzle the savory peppercorn sauce over the steaks and serve immediately.