Preheat the oven to 180°C (350°F) and line a baking tray with parchment paper.
Unroll the puff pastry on a lightly floured surface.
Using a coffin-shaped cookie cutter, cut out about 20-24 coffin shapes.
On half of the coffins, use a small cross-shaped cutter to create a window in the centre — these will be the tops.
Place the remaining 10-12 solid coffin shapes on the prepared tray.
Spoon a small amount of chocolate sauce onto the centre of each base and spread it slightly (leaving the edges clear).
If using, brush the edges with beaten egg to help seal.
Top with the “cross-window” pieces and gently press the edges together with a fork.
Brush the tops with the remaining egg wash for a golden finish.
Bake for 10–12 minutes, or until puffed and golden brown.
Dust lightly with cocoa powder or cinnamon before serving.
Serve on crumbled chocolate cookies to look like soil, and add tiny sugar skulls or candy bones for extra spooky effect!