To ensure the pastry is fully/correctly proofed before baking, there are visual clues which indicate when the pastry is ready to bake. The first visual clue is when air spaces appear between the layers of the pastry running right through the pastry from the outside to the core. Remember, that the core of the pastry is where the temperature takes the longest to be penetrated by the heat of the proofer. If not correctly proofed, the pastry will have a dense, gummy core. Viennoiserie will always proof from the outside to the centre. Coiled and high pastry such as croissant and pain au chocolat will always take at least two hours to proof under normal proof conditions (26−27ºC). Coiled, but flatter pastries, such as pain aux raisins, cinnamon rolls or those cut with cutters, such as the pear pastries page 134 will proof faster as they are not as thick or high. Pay particular attention to the innermost fold, the start of your pain au chocolat coil in the very centre, if there is good separation, and it is not gummy at the core, you are nearly there.
The “Wobble Test” is the other visual clue where, when the tray is gently shaken, the entire pastry quivers like a bowl of jelly. You can see an example here:
Further details available in my book, The Art of Lamination: Advanced Technical Laminated Pastry Production.