In a medium saucepan, heat the peanut oil until shimmering. Add the shallot and garlic and cook over moderate heat, stirring, until golden, about 3 minutes. Remove from the heat and whisk in the coconut milk, peanut butter, brown sugar, chili-garlic sauce and ginger. Gradually whisk in the water. Simmer the sauce over moderately low heat until slightly thickened, about 10 minutes. Let cool slightly, then whisk in the lime juice and peanuts. Season with salt. Transfer the sauce to a bowl or a glass jar and serve warm, at room temperature or chilled.