Squashsuppe

Peel, seed, and cut the squash into 2-cm cubes, removing the tough outer skin and stringy centre.

Heat butter and oil in a large pot over medium heat until the butter is melted and foaming.

Add chopped onion and sauté, stirring occasionally, until softened and translucent.

Add squash cubes to the pot and stir to coat with the butter-oil mixture.

Pour in chicken stock and bring to a boil, then reduce heat and simmer until squash is completely tender and falls apart easily.

Remove pot from heat and let cool slightly, then blend soup until smooth using an immersion blender or by carefully transferring batches to a food processor.

Return soup to medium heat and stir in basil, then season with salt and pepper to taste.

Whisk egg yolks in a small bowl, then temper them by slowly adding a ladle of hot soup while whisking constantly to prevent curdling.

Pour the tempered egg yolk mixture back into the pot while stirring constantly, then cook gently without boiling until slightly thickened.

Ladle soup into bowls and garnish each serving with grated Parmesan cheese.