One of the biggest problems for a professional pastry kitchen is dealing with leftovers. It's an issue I have to address much less as a home cook, unless I'm catering for a large group of friends and make too much (which happens often). However, while my friends are happy to take any extra cakes, tarts and cookies off my hands, in professional kitchens there's pressure to turn leftovers into something that will make money and lower costs.
When I was doing my pastry apprenticeship in hotels in the United States, we'd cater for breakfast meetings and lunch and dinner banquets. The desserts left over from the lunches and dinners were easy to get rid of: we'd give them to the staff canteen so other employees could enjoy them. But the sheer volume of croissants, Danish pastries and muffins left over from breakfast meetings presented a problem - even the staff got tired of them.
So, we'd "repurpose" the pastries. Some of the croissants were split in half, brushed with almond syrup and sandwiched with almond cream, then sprinkled with sliced almonds and baked. They became croissants aux amandes and could be served at break-fast meetings the following day. Other croissants, as well as the cheese-, custard- and fruit-filled Danish pastries, were cut into large cubes then mixed with eggs, milk, cream and sugar and baked into bread pudding, which was a popular dessert for banquets when served with whisky sauce and crème anglaise.
Everything else we dried out in the oven, then ground up to make "crumbs". These crumbs had many uses. We pressed them onto the sides of iced cakes, to decorate them; we used them instead of breadcrumbs in strudel, sprinkling them over filo sheets that had been brushed with butter, so the crumbs would soak up the juices from the apples we rolled inside the layers; and we mixed them with melted butter and pressed them into spring-form pans to create bases for cheesecake.
The majority of the crumbs, however, were used in tortes and rum balls, which were made in a similar way: mix the crumbs with ganache (an emulsion of melted chocolate and cream) until they make a thick paste, then flavour it with rum (for the rum balls), or anything from raspberry jam to coffee to other types of alcohol (for the tortes).
We'd shape the rum-ball mixture between the palms of our hands until the balls were slightly bigger than chocolate truffles, roll them in cocoa powder and put them in chocolate paper cases. These were very popular as part of the Sunday brunch buffet.
For tortes, we'd press the crumbs and ganache mixture in thin layers in cake pans, then refrigerate until firm. After turning the layers out of the pan, we'd cover them with mousse then ice them with melted ganache. This was another popular dessert - and nobody ever had a clue that it was made with leftovers.
Truc (tryk): noun, masculine, trick, gimmick, device. A French word for a chef's secret.