Preheat oven to 210 °F (100 °C).

Beat the egg whites with the confectioner’s sugar in a bain-marie until it is not so airy, but is creamy.

It should be between 113 and 122 °F (45 and 50 °C).

Then beat in an ice bath until it cools.

It should thicken without losing volume.

Fill a piping bag fitted with a round nozzle and line a baking sheet with parchment paper.

To make the mushroom stems, press the piping bag nozzle against the parchment paper and pull it up without squeezing any more.

For the mushroom tops, pipe semicircles and dust them with cocoa powder before baking.

Dry in the oven for 30 minutes