How to Make It
In a large skillet, melt the butter. Add the onions and cook over moderately low heat, stirring occasionally, until softened, about 30 minutes. Add the thyme, sage, nutmeg and white pepper and cook, stirring, for 2 minutes. Add the cream and bring to a boil. Simmer over low heat, stirring occasionally, until thickened, about 5 minutes. Season with salt, transfer to a bowl and serve.