Peel the onions and cut into quarters or eighths. Fry in the butter for 2-3 minutes, add the fondor, sugar, water, garlic and caraway seeds and cook covered for about 20 minutes.
Whisk the cream and egg yolk with the cornstarch, mix with the onions, bring to the boil and immediately remove from the heat.
Mix in the parsley and season with salt and pepper.