Prepare the base: In a medium saucepan, whisk together eggs, sugar, vanilla sugar, and cornstarch until smooth and lump-free.

Add the milk: Gradually pour in the milk while whisking constantly. This prevents lumps and ensures a smooth texture.

Cook the mixture: Place the saucepan over medium heat and cook while stirring continuously until the cream thickens — this usually takes about 7–10 minutes. The consistency should be like thick custard.

Add lemon flavor: Once thickened, remove from heat. Stir in the grated lemon peel and freshly squeezed lemon juice. Mix well until fully incorporated.

Cool slightly: Let the cream cool for about 10–15 minutes, stirring occasionally to prevent a skin from forming.

Add mascarpone: Once the mixture is warm (not hot), fold in the mascarpone cheese using a whisk or spatula until smooth and creamy. The mascarpone adds richness and a silky texture.

Chill: Cover the cream with plastic wrap (pressing it directly on the surface) and refrigerate for at least 1 hour before using.