Start by crushing your black peppercorns using a mortar and pestle or pepper mill. I like mine coarse for extra punch. Season the steak on both sides with kosher salt and a generous layer of crushed pepper. Press the seasoning in gently so it sticks well.
Heat olive oil in your Dutch oven until it shimmers. Add the steaks and sear one side for about 3 minutes. Flip them, add the butter and thyme sprigs, and baste with the melted butter for another 2–3 minutes. Once both sides are beautifully crusted, set the steak aside to rest. Strain and save the flavorful fat left in the pot.
Wipe out any burnt pepper bits, then return the reserved fat to the pot. Add chopped shallots and sauté until soft. Stir in garlic and a few thyme leaves. Once fragrant, sprinkle in the flour and whisk until it’s slightly golden. This thickens your soup base perfectly.
Pour in your cognac slowly while whisking—it’ll bubble up! Then, add beef broth gradually, whisking to keep it smooth. Toss in your halved baby potatoes and bring the soup to a gentle simmer. Let it cook for about 15 minutes until the potatoes are fork-tender.
Lower the heat and pour in the heavy cream and Worcestershire sauce. Stir well and let the soup warm through for about 5 minutes. The smell at this point is amazing—creamy, peppery, and rich.
While the soup finishes, heat olive oil in a small pan and fry sliced shallots until golden and crispy. I drain them on a paper towel to keep them crunchy.
Cut the rested steak into bite-sized cubes. Ladle the soup into bowls and top with steak cubes and crispy shallots. Sprinkle with Parmesan and lemon zest if you like—it makes each bowl feel fancy.