In a saucepan, melt the butter over low heat.
Add the onion juice and cook until the onion begins to color.
Stir in the flour and curry powder, cooking until the mixture is smooth and fragrant.
Gradually pour in the clear stock while whisking constantly to avoid lumps.
Add the heavy cream and continue cooking for about 5 minutes, stirring constantly, until the sauce thickens.
Season the sauce with salt and pepper to taste.
Cut the hard-boiled eggs in half lengthwise and arrange them in a serving dish.
Pour the curried sauce over the eggs, ensuring they are evenly coated.
Let the dish stand on low heat for a few minutes until the eggs are thoroughly heated.
Serve the curried eggs on thin squares of toast.