Preheat the oven to 400°F (200°C).

In a small bowl, combine the espresso powder, ground cinnamon, brown sugar, salt, and black pepper. Mix well to create a spice rub.

Pat the porterhouse steaks dry with paper towels. Rub the olive oil over both sides of the steaks, then generously coat them with the espresso and cinnamon spice rub.

Heat a large oven-safe skillet over medium-high heat. Once hot, add the steaks and sear for 4-5 minutes on each side until a nice crust forms.

Transfer the skillet to the preheated oven and roast for about 10-15 minutes for medium-rare, or until the desired doneness is reached. Use a meat thermometer to check (130°F/54°C for medium-rare).

While the steaks are in the oven, prepare the whipped brown butter jus. In a small saucepan, melt the butter over medium heat. Continue cooking until the butter turns golden brown and develops a nutty aroma, about 5-7 minutes. Be careful not to burn it.

Once the butter is browned, remove it from heat and stir in the beef stock. Simmer for a few minutes until slightly thickened. Season with salt and pepper to taste.

Once the steaks are done, remove them from the oven and let them rest for 5-10 minutes before slicing.

Slice the porterhouse steaks against the grain and arrange them on a serving platter. Drizzle the whipped brown butter jus over the steaks and garnish with fresh herbs.

Serve immediately and enjoy!