Preheat the oven to 200ºF. Line 2 baking sheets with parchment paper.

Place the egg whites in the bowl of a stand mixer. Add the vanilla extract, cream of tartar, and salt.

Turn the mixer to high speed and let it mix until foamy. Once foamy, start adding in the sugar, 1 tablespoon at a time, while the mixer is still on. Keep beating until the mixture forms very stiff, glossy peaks, about 5 minutes.

Transfer the mixture to a piping bag that is fitted with an Ateco 804 or Wilton 2a tip. (You can do this without a tip by just cutting the corner of the bag, but I find it is much harder to shape the meringues without a tip.) You may also need to do this in batches, depending on how big your piping bag is.

On the prepared baking sheets, pipe an equal number of stems and mushroom caps. For the stems, the base should be about 1/2” wide and taper up to a point. For the caps, they should be a dome about 1 1/4” in diameter. If there is a point on top of the domes, you can use a wet fingertip to smooth it out. You should get anywhere between 30-45 stems and mushroom caps, depending on the size that you make them.

Transfer the baking sheets to the oven and cook, without opening the oven, for one hour. Turn off the oven and let them sit, (again, without opening the oven), until they are completely cooled. I like to leave them in the oven overnight, but they should be cool in a couple of hours.

When ready to assemble, turn all of the caps upside down, so the flat side is up. Use a small paring knife to carefully make a hole in the flat side of each mound.

Melt the chocolate chips until smooth. Dip the pointed end of a stem into the chocolate, then gently press that into the small hole in the cap. Hold it for a few seconds until the chocolate has set. Place the mushroom back on the baking sheet for the chocolate to continue to harden.

Once all of the mushrooms are assembled, dust them with cocoa powder.