Preheat oven to 375 degrees F.

Combine cocoa powder, brown sugar and remaining rub seasonings in a small bowl.  Drizzle 2 tablespoons of olive oil over both sides of the tenderloins (reserve remaining olive oil for later). Sprinkle cocoa spice rub over tenderloins and use your hands to coat both sides evenly.

Place potatoes on a large rimmed baking sheet, drizzle with olive oil, season with salt and pepper and toss to coat. Place on lower rack of preheated oven. Roast for 20 to 25 minutes, or until tender and golden brown. Use a spatula to stir once or twice during cooking time.

Meanwhile, place a large oven-proof skillet (cast iron works well) over MEDIUM-HIGH heat. Add remaining two tablespoons olive oil to the skillet and when hot, add seasoned pork. Sear for 2 to 3 minutes per side, or until nicely browned.

Transfer skillet to preheated oven on rack above potatoes and roast for 15 to 20 minutes or until pork has reached an internal temperature of 150 degrees F when measured with an instant read thermometer in thickest portion of the tenderloin. Remove skillet from oven, transfer tenderloins to a cutting board and cover loosely with foil to keep warm.

Pour off all but about 1 tablespoon of the drippings from the skillet and place skillet over MEDIUM heat. Add red wine, whisking to loosen any browned bits from bottom of skillet. Bring to a boil; reduce heat to MEDIUM-LOW and simmer for 2 to 3 minutes at a low boil to slightly reduce the wine. Meanwhile, combine 1 tablespoon softened butter with flour in a small bowl. Add beef broth and tomato paste to the sauce and whisk until completely incorporated. Whisk butter/flour mixture into the sauce and continue whisking until sauce is just slightly thickened. Add 2 teaspoons of cold butter and stir until butter melts and sauce is glossy.

Slice tenderloins and transfer to a serving platter. Scatter roasted potatoes around pork and garnish with chopped fresh parsley. Drizzle a little of the pan sauce over the pork and serve with additional sauce on the side.