Heat the oven to 425 degrees F.

Unfold the pastry sheet on a lightly floured surface. Roll the pastry sheet into a 12-inch square. Cut off the corners to make a circle. Press the pastry into the bottom and up the sides of a 9-inch springform pan. Prick the pastry with a fork.

Bake for 20 minutes or until the pastry is golden brown. Let the pastry cool in the pan on a wire rack for 10 minutes.

Heat and stir the chocolate and cream in a 1-quart heavy saucepan over low heat until the mixture is melted and smooth. Remove the saucepan from the heat. Stir some chocolate mixture into the egg yolk. Return the egg mixture to the remaining chocolate mixture. Cook and stir for 1 minute. Pour the chocolate mixture into the pastry crust. Cover and refrigerate for 2 hours or until firm. Top the torte with the raspberries.

Stirring a bit of the warm chocolate mixture into the egg before adding it to the rest of the chocolate is an important step called "tempering". Tempering keeps the egg from scrambling and the filling smooth.