Pork is one of the most popular meats of the Basque country. (Lamb is another.) Walnuts are a local product, and cooks on the Spanish side of the border often make nut sauces like this one.Plus: More Pork Recipes and Tips
Preheat the oven to 300°. In a food processor, combine the walnuts, almonds, garlic and coriander seeds and add 1/4 cup of the olive oil. Pulse just until the mixture resembles a coarse pesto.
Cut the tenderloins into 3/4-inch-thick medallions and season with salt and pepper. In a large skillet, heat the remaining 2 tablespoons of olive oil. Add half the pork medallions and sauté over moderately high heat until well browned and just cooked through, 2 to 3 minutes per side. Transfer to a large plate and keep warm in the oven. Repeat with the remaining pork medallions.
Add the wine and shallot to the skillet and cook over moderately high heat, scraping up any browned bits from the bottom of the pan. Add the sage leaves and boil until the wine is reduced by half, about 3 minutes.
Add the veal stock and the crushed nut mixture to the pan and stir until warmed through. Season with salt and pepper. Transfer the pork to large plates, drizzle with the nut sauce and serve.