Fit a medium sized piping bag with a ½” plain tip, and have it propped up in a drinking glass. For more details on setting it up, see this post on how to use a piping bag.

Put the egg whites into the bowl of a stand mixer fitted with a whisk attachment, and beat on medium-low until the whites look very frothy, about 3 minutes. Add the lemon juice and salt, then increase the speed to medium.

When the egg whites can hold soft peaks, begin sprinkling in the sugar a little at a time; it should take about a minute to add it all. Increase the speed to medium high, and continue whipping until the meringue is thick and can hold very stiff peaks.

Add the vanilla bean seeds and a tiny speck of brown gel paste, if using, and whip until well combined. That microscopic splash of color (only what will stick to the tip of a toothpick) prevents the mushrooms from turning out shock-white. In the bowl, you won’t even notice a color change, but it really helps!

Transfer half the meringue to a piping bag.

To pipe the mushroom caps, hold the piping bag a ½” above the baking sheet and give the bag one good squeeze. Relax your grip, lift the piping tip slightly, and jerk the tip quickly to one side (this breaks the meringue “tail,” so the cap doesn’t have a peak or curlicue on top).

Pipe an assortment of caps, from tiny ½” babies to bigger 3” discs, until you run out of meringue.

Put a little water in a dish, and use a damp fingertip to smooth out any peaks so the caps are smooth and round.

To pipe the stems, refill the bag and hold it as before. As you begin to squeeze, slowly lift the bag straight up. After about 1”, stop squeezing, but keep lifting the bag up, up and away. Pipe an assortment of stems, some short and squat and some tall and skinny, and some kinda knocked over to the side. Continue piping until you have a few more stems than caps, to account for breakage.

If you have extra meringue at this point, pipe more caps and stems to polish it off.

Bake the meringues until bone dry, about 90 minutes. Cool the meringues to room temperature before proceeding.

Using a fine mesh sieve, lightly dust the mushrooms caps with cocoa powder. Rub the cocoa into the meringue, using your fingertips to smudge it around. Repeat the dusting and rubbing procedure at least one more time. Once you’ve got a nice base color, you canstrategically darken the caps here and there to make them look more natural.

Now, use your cocoay fingerstips to smudge up the stems too. They should be lighter than the caps overall, so you don’t need to sprinkle them with cocoa directly. Just dip your fingertips into a patch of cocoa from time to time to keep ‘em dusty. While you smudge the stems, use your fingers to break of the tip of each one, so it’s flat on top.

Save all the crumbled meringues in a little pile (for the moss).

I like using melted white chocolate to assemble the mushrooms, because it looks almost invisible, but feel free to use dark chocolate if you’d rather. Dip the very tip of each stem into the chocolate, then stand it upright on a baking sheet and place a mushroom cap firmly on top. If a mushroom needs support, scoot it to the edge of the baking sheet so it can rest again the rim while the white chocolate hardens.

Meanwhile, transfer the meringue crumbles (and any broken caps or stems) to a small zip-top bag, along with a few teaspoons of Matcha. Shake until the crumbs are evenly coated, then use as “moss” to garnish your Yule Log.

To keep your creations safe, make a little Mushroom Crate by lining an egg carton with plastic wrap. Nestle a mushroom or two into each cubby, then carefully wrap the whole thing in plastic and set aside in a cool, dry place.

The meringue mushrooms will keep for a week or two.