Finely chop the onion, peel and squeeze the garlic. Sweat both in butter, dust with the flour and stir. When the flour turns slightly brown - deglaze immediately with white wine and stir vigorously with a whisk. Pour 1/4 L water on and bring to the boil. Remove from heat and puree with a hand blender. Then add the rest of the water and milk, bring to the boil and then simmer on a low level for about 10 minutes. Add the stock cube and season with salt, pepper, cayenne pepper and nutmeg.