Place one puff pastry sheet on a flat surface. Brush with beaten egg. Top with another pastry sheet. Brush again with egg. Top with the 3rd pastry sheet.
Use a large cookie cutter to cut out 9 circles out of the pastry sheet. Use a small piping nozzle to cut out smaller circles from the center of each large circle.
Arrange the circles on a lined baking tray. Brush again with beaten egg. Bake at 200C or 400F for about 20-25 minutes. Roll the cronuts in cinnamon sugar, drizzle with melted chocolate and dip in sprinkles.