Mix 2 tablespoons each grated ginger, finely chopped ginger and finely chopped scallion in a small bowl. Add 1/2 teaspoon kosher salt and 1/4 teaspoon white pepper. Heat 3 tablespoons vegetable oil in a small saucepan until smoking; pour over the ginger-scallion mixture and stir. Add a splash of water if the sauce is too thick. Season with salt.