Sporcamuss

Bake the puff pastry

1. Defrost the puff pastry following the directions on the package. Make sure it's still cold.
2. Lay the defrosted pastry sheet on a board and cut it into squares about 6cm by 6cm (roughly 2-1/3"x2-1/3"). Place the squares on a baking sheet lined with parchment paper, spacing them well. Brush with the egg wash.
3. Bake in a hot (200C/400F) oven for about 10-15 minutes, or until puffed up and golden brown.
4. Take the baking sheet out of the oven and let the pastry squares cool on a baking rack.

Make the filling

1. In a standing mixer bowl, whisk together the egg yolks and sugar until smooth and the mixture forms ‘ribbons’ as the whisk rotates. Then add the flour or cornstarch slowly, bit by bit, into the mixture until fully incorporated. The mixture should be a pale yellow and quite fluffy.
2. Meanwhile, heat the milk (or milk and cream) over moderate heat until hot but not boiling. You will see little bubbles just beginning to form around the edge of the pot. (If you are using a vanilla bean, add it to the milk and let it steep for a few minutes, then remove it.) Take the milk off the heat and drizzle it, little by little, into the mixer bowl.
3. Now pour the whole thing from the bowl into the pot (along with the vanilla extract if using) and put it over very gentle heat, whisking continuously and vigorously. After a while, it should begin to thicken. Keep stirring until you have a thick custard.
4. Remove from the heat, stir in the grated lemon zest if using, and let the mixture cool. It will thicken further as it cools.
5. When the custard has cooled completely, whip the cream with the powdered sugar until it forms stiff peaks. Fold it into the custard until you have a uniformly fluffy consistency.

Filling the puff pastry

1. Take each puff pastry square and, with the aid of a paring knife, very gingerly split their tops from the bottoms and pry them open.
2. Using pastry bag (or just a plastic bag clipped on its corner) cover the bottom of the puff pastry square with a thick piping of the pastry cream. Then replace the top pressing it down gently so it adheres to the filling to form a little sandwich.

Serving

1. Dust your sporcamuss with confectioners sugar and serve.