Chestnut Cream Filling

Score the skin of each chestnut with a sharp paring knife.

Bring a large pot of water to a boil. Add chestnuts and cook for 25 minutes. Drain.

Peel chestnuts while still warm. Transfer to a food processor. Add 1/4 cup powdered sugar, 2 tablespoons butter, and 4 1/2 tablespoons heavy cream; puree until smooth.

Combine remaining 2 1/2 tablespoons heavy cream, white sugar, egg yolk, vanilla extract, and salt in a large bowl. Beat until quite thick, 6 to 7 minutes.

Beat remaining 8 tablespoons butter in a small bowl until light and fluffy. Slowly mix into the egg mixture. Gradually beat remaining 2 3/4 cups powdered sugar into the egg mixture.

Stir chestnut puree into the egg mixture, making sure to blend in well.