Preheat the oven to 425 °F.
Rub the sweet potatoes with 1 tbsp oil and season with ¼ tsp salt.
Place on a parchment lined baking sheet, cut side down, and roast for 30 to 35 minutes, until very soft.
While the sweet potatoes are roasting, make the salsa.
Put the remaining 3 tbsp oil into a small bowl with the basil, parsley (or cilantro), garlic, lime zest, lime juice and a good pinch of salt, and stir to combine.
Once cool enough to handle, remove the skin from the sweet potatoes. They should slide easily, but you can scoop the flesh with a spoon if you prefer. Mash the flesh together with ⅛ tsp of salt and plenty of black pepper until smooth.
Transfer to a platter, create divots in the surface, and spoon the salsa evenly over. Serve hot.
