I had never heard of a pièce montée before coming to France, but here it is quite traditional. It is a dessert, often served as part of a formal meal, usually one with a celebratory or religious function. Basically it's a big stack of profiteroles arranged into a cone, and decorated with sugar figures and shapes. When used, it takes the place of a fancy cake.
We catered a wedding party last weekend, and it featured a pièce montée. The meal started with champagne and nibbles, continued with a starter of seafood terrines, then on to a fish course (cod in papillotte), a steak main course, cheese, and the final pièce montée. A fantastic meal, it lasted from about 7:30 until 1:00 am, and everyone loved it. Very pleasing to cater at such a high level, and to everyone's satisfaction.
The tables all laid out with flowers, and the starter course ready to go.
The cheese course, and the pièce montée. You can't see it well in the photo but the sugar sculpture on top is a bride and groom figurine. The choux-pastry balls, (not very visible in the photo since they are mostly covered by the hearts and other decorations,) are stuck together with a sugar syrup/caramel glue, and you have to cut them apart with scissors.