Preparation of the Triangles:

1. Cook the potatoes: Boil the potatoes in salted water until tender. Let them cool down.
2. Sauté the leeks and onions: Sauté the leeks and onions in some butter until they are well reduced and soft. Season to taste.
3. Add the cream: Pour the cream into the leek-onion mixture, reduce slightly, then allow it to cool down.
4. Combine the mixture: Once the mixture is cooled, fold in the leeks, potatoes, and Gruyère AOP. Season with salt and pepper to taste.
5. Shape the spring rolls: Lay a slice of turkey ham on each spring roll wrapper and fold it into triangles, similar to samosas.
6. Bread the triangles: Coat the triangles first in flour, then dip them in beaten egg, and finally coat them with breadcrumbs.
7. Fry the triangles: Fry the triangles in a deep fryer at 180°C for 5-7 minutes until golden brown. Drain well and serve.

Preparation of the Calypso Sauce:

1. Make the mayonnaise: Whisk the egg yolk with mustard and vinegar (or lemon juice) in a bowl. Slowly drizzle in the sunflower oil while whisking continuously. If the mayonnaise becomes too thick, add a small amount of water to loosen it.
2. Make the ketchup: Combine all ingredients for the ketchup in a saucepan. Cook over medium heat for 5 minutes, then let it cool down.
3. Finish the sauce: Mix the mayonnaise with the ketchup to taste and add finely chopped garlic. Season as desired.