What French technique cooks food in a sealed paper packet?

What French technique cooks food in a sealed paper packet? En papillote is the French method of baking food inside a tightly sealed parcel.

The parcel is traditionally made from folded parchment paper. Fish, vegetables, poultry, or other ingredients are enclosed with seasonings and sometimes wine, water, or stock before being baked. Heat turns the liquid and the food’s own moisture into steam, so en papillote combines the effects of baking and steaming.

The technique has been popular in France since at least the 17th century. A well-sealed packet traps aromatic vapours, helping ingredients cook gently while retaining moisture. The packet is often opened at the table, releasing a dramatic cloud of steam and the concentrated aroma of herbs, citrus, and other seasonings.

Aluminum foil can be used, although parchment is the traditional material. In Italian cooking the same general approach is called al cartoccio. En papillote is not sous vide: sous vide uses a sealed bag immersed in a controlled water bath, whereas en papillote is normally baked in a pouch.