SERVES 4
The humble and ancient chestnut was once fundamental to the Galician diet, though it was largely displaced by the sixteenth-century introduction of potatoes (and corn). A favorite way to cook them is as a purée to accompany roasted or grilled meats and sausages.
Searing the tenderloins will keep them juicy and tender. Be sure to turn them with tongs, not with a fork, which will release some juices.
1. Peel the chestnuts: Score the flat side of the chestnuts with a short, cross-shaped incision through the leathery surface using the tip of a sharp knife. Bring a saucepan filled with water to a rolling boil. Drop in the chestnuts and boil for 2 to 3 minutes. Fill a bowl with cold water. Transfer the chestnuts with a slotted spoon to the cold water. Cover the saucepan and keep the water at a low boil. Once the chestnuts are cool enough to handle, take them from the water one by one and peel away both the outer layer and the thin, membrane-like inner one that covers the nut. Use a paring knife if needed to help. If the inner covering does not easily come away, drop the chestnut back in the boiling water for 1 minute, transfer with a slotted spoon to the bowl of cold water to cool, and then peel. Place the peeled chestnuts on paper towels to dry. There should be about 10 ounces/280 g of peeled chestnuts.
2. In a saucepan, add the milk and chestnuts, cover the pan, bring to a simmer over medium heat, and simmer until the chestnuts are tender, about 30 minutes. Purée them in the pan with an immersion hand blender or transfer to a food processor, purée, and then return to the pan. Stir in the butter, brandy, and a pinch of salt and cook, stirring continually, over low heat for 2 to 3 minutes to burn off the alcohol. The texture should be creamy and thickish; it will thicken a bit more as it cools. (Add a touch more butter if necessary.) Remove from the heat.
3. Meanwhile, preheat the oven to 350°F/180°C/gas mark 4.
4. Preheat a grill pan, griddle pan, or large, heavy skillet over high heat, lightly oil, and scatter with salt flakes. Lay the tenderloins in the pan and quickly sear, turning with tongs as needed, until they are browned and have a slight crust, about 5 minutes.
5. Transfer the pork to a roasting pan, slide it into the oven, and roast until done and the insides are still rosy, 15 to 20 minutes, depending on the thickness of the tenderloins. An instant-read thermometer poked into the center of the tenderloin should read at least 145°F/63°C. Drizzle with the sherry about halfway through cooking.
6. Transfer the loins to a cutting board and let rest for 3 minutes before slicing into generously sized medallions, about two or three fingers thick. Arrange a couple of medallions on each plate, sprinkle with salt flakes, and garnish with a generous dollop of the purée of chestnuts. Serve with the remaining purée in a bowl on the side.