Preheat your oven to 400°F (200°C). Place the bone marrow in a small baking dish and roast for about 15-20 minutes until it is bubbly and golden. Remove from the oven and let it cool slightly.

In a small saucepan, melt the unsalted butter over low heat. Add the fresh sage leaves and let them infuse for about 5 minutes. Remove from heat and strain the butter through a fine mesh sieve to remove the sage leaves. Set aside.

In a bowl, mix the crushed pistachios, smoked cardamom, and smoked sea salt. Pat the filet mignon steaks dry with paper towels. Season both sides of each steak with freshly ground black pepper. Rub the olive oil over the steaks and press the pistachio mixture onto one side of each steak, ensuring an even coating.

Heat a skillet over medium-high heat. Once hot, place the filet mignon in the skillet, crust side down. Sear for about 3-4 minutes until a golden crust forms. Flip the steaks and cook for an additional 3-4 minutes for medium-rare, or adjust according to your desired doneness. Transfer the steaks to a plate and let them rest for 5 minutes.

To serve, place a dollop of whipped bone marrow on each plate alongside the filet mignon. Drizzle with sage butter and garnish with additional crushed pistachios if desired.