Make the Craquelin: In a mixing bowl, combine flour, brown sugar, and a pinch of salt. Knead in softened butter until you achieve a smooth, pliable dough. Roll the dough between two sheets of parchment paper into a thin layer, freeze for 30 minutes.

Prepare Choux Pastry: Preheat your oven to 355°F (180°C). In a saucepan, combine water, butter, and a pinch of salt. When melted and boiling, add all-purpose flour and stir until a smooth dough forms. Cook for 2-3 minutes, then let it cool slightly.

Incorporate Eggs: After the mixture has cooled for 10 minutes, beat 4 eggs and gradually add to the dough, mixing well after each addition until shiny and smooth.

Pipe Choux Puffs: Fill a piping bag with the choux pastry. Pipe small mounds on a baking tray, spaced 2 inches apart. Cut discs from the frozen craquelin and place on top of each mound.

Bake: Bake for 35-40 minutes until golden brown and firm. Do not open the oven door during baking. Let cool on a wire rack.

Prepare the Filling: Simmer milk with sugar and split vanilla bean. Whisk cornstarch and egg yolks in a separate bowl. Combine mixtures, return to stove until thickened, add gelatin, and cool completely.

Assemble: Fill cooled choux with vanilla bean pastry cream using a piping bag. Dust with powdered sugar before serving.