1. Separate the egg yolks from the egg whites.
2. Whisk the egg yolks with the sugar, add the flour, then fold in the beaten egg whites with the vanilla sugar.
3. Pour the batter onto a baking sheet lined with parchment paper, spread it out with a spatula, and bake for 10 to 12 minutes in a preheated oven at 200°C (400°F).
4. Flip the biscuit onto a damp cloth, roll it up, and set aside.
5. Whisk the mascarpone cheese and powdered sugar together.
6. Blend the pistachios with 1 tablespoon of powdered sugar.
7. Unroll the biscuit, spread a layer of mascarpone cheese, sprinkle with pistachios, distribute the raspberries, and tightly roll up the yule log.
8. Wrap it in plastic wrap and refrigerate for 4 hours or more.
9. Dust with powdered sugar before serving.