MAKE THE BEEF

1. Preheat the oven to 425 degrees F.
2. Dry beef thoroughly with paper towels. 
3. Rub with olive oil and season with salt & pepper. 
4. Let sit at room temperature for 45 minutes. 
5. In a large skillet (preferably cast iron) heat until good and hot. 
6. Add the meat and sear until well browned on all sides, about 10 minutes total.
7. Transfer the meat to a rack set on a baking sheet. 
8. Lay whole springs of rosemary over the roast and tie with kitchen twine at 1-inch intervals (Note: may need to cut slit to tuck the tail end under the roast to give more uniform thickness)
9. Roast until an instant-read thermometer inserted in the thickest part registers 120 degrees F for medium-rare, about 30 minutes, or to your desired degree of doneness. 
10. Remove it from the oven, lightly tent with aluminum foil, and let rest until the sauce is nearly done before slicing (internal temp will rise to about 130 for medium-rare)

MAKE THE COMPOUND BUTTER

1. Heat the remaining 2 teaspoons of oil in a large saucepan over medium-high heat. 
2. Add the shallots, carrot and celery and cook, stirring a few times, until softened, about 5 minutes. 
3. Add the garlic and cook for 2 minutes more. 
4. Add the wine and broth and stir in the tomato paste. 
5. Add the bay leaf and thyme and bring to a boil. 
6. Simmer until the liquid is reduced to about 1/2 cup, about 40 minutes. 
7. Strain through a fine mesh strainer into a small saucepan. 
8. Stir in the cocoa and rosemary and season with salt and pepper.
9. Serve on the side with the sliced tenderloin.

MAKE THE PORT REDUCTION

1. Heat the veal stock in a medium saucepan to a boil. Reduce by half until thick and syrupy to make veal demi-glace.
2. Add the reduced port to the demi-glace and bring to a simmer. 
3. Remove from heat.
4. Strain through a fine chinois into a bowl.