The double chocolate twin laminated pastry is a chocolatine, coiled style pastry made with two types of laminated croissant pastry pinned together to a thickness of 3.5mm. Two croissant bars are used inside the pastry as is typical for chocolatine, and the pastry can be dusted with dark cocoa or icing sugar after cooling. To make an even crispier pastry, this one is typically scored several times before rolling. Scoring creates more surface area in the pastry. The layers open out during the proof stage and increase the surface area of crispy layers.
Here’s a time-lapse video which demonstrates the science behind chocolatine:
Chocolatines are a coiled pastry with one large or two smaller chocolate bars inserted in the centre. They are generally made using a 3-4-4 Lamination system -33 alternating layers of dough and butter. During this time lapse video , the 20-minute bake time is condensed into 35 seconds. As the heat of the oven penetrates the pastry, two things happen: the fermented dough has CO2 gas bubbles (a by-product of fermentation) trapped in the gluten matrix. The gas expands when heated causing the bubbles to inflate the pastry. Secondly, the water in the dough begins to vaporise into steam causing further expansion. You can see in the video how the pastry layers expand and also how the coil from the centre unfolds slightly. The chocolate, under the power of gravity starts to sink downwards as the pastry expands upwards and outwards. The additional tension and layers in the dough give a more rounded chocolatine when made with the 3-4-4 system. After several minutes, the expansion of the pastry slows down as crust formation begins on the outer surfaces. As the heat penetrates to the core of the pastry, the pastry begins to firm up in the centre as the moisture is driven out during the bake. Towards the end of the video you can see there is no further expansion of the pastry and the pastry becomes fully baked. Timing and temperature are important as if the temperature is too high, the outside will appear to be baked, but the core will remain gummy / doughy in the centre. Too low a temperature will result in the pastry not colouring and it will take longer to bake, drying out the pastry.
My full recipe and more tips are available in my book, The Art of Lamination: Advanced Technical Laminated Pastry Production.