Step 1

Prep: preheat the oven to 225°F with the oven rack centered. Line a baking sheet pan with parchment paper or a silicone mat. Fit a large pastry bag with a 1/4" plain round piping tip. Set aside.

Step 2

Make the meringue: to a bowl of a stand mixer, add 2 egg whites, 1/2 cup sugar, and a pinch of salt. Whip on medium speed until glossy, stiff peaks form, about 20 minutes. When you dip a whisk into the meringue and quickly lift it, the tip of the meringue should form a "beak" that only slightly bends or doesn't bend at all.

Step 3

Pipe: fill the prepared pastry bag with the meringue. Pipe the mushroom stems first. Next, point the piping tip directly over the parchment paper. Start squeezing the meringue by touching it to the parchment paper, then slowly raising the bag as you squeeze forming a stem or a cylinder. Use scissors to "cut" the top of the stem flat. Space all cookies about 1 inch apart as you pipe them.Pipe caps by piping kisses or disks about 1 1/2 - 2 inches round.

Step 4

Decorate: sprinkle red sprinkles over the caps of the mushrooms.

Step 5

Bake in the oven until completely dry, about 1 hour. Remove from the oven and cool completely.

Step 6

Make the stem tops flat: Use the fine side of the grater and gently file the top portion of the stems flat. This will make it easy to join the stems to the cap.

Step 7

Melt the chocolate: place white chocolate, and dark chocolate melts into two separate small bowls. Heat in the microwave in 5-10 second increments, stirring after each until about 3/4 of the chocolate melts are melted. Then, continue stirring until all chocolate is melted.

Step 8

Join stems to caps: dip the tops of the stems into a tiny amount of chocolate and quickly put a mushroom cap on top. Press briefly to allow the two to glue. Set them on an even surface until the chocolate solidifies. Repeat with the rest of the meringue mushroom pieces.

Step 9

Decorate: use a pastry brush to brush on some cocoa powder all over the mushrooms to give the meringue mushrooms a rustic and realistic feel. Or, use a small brush to paint the bottom of the meringue mushrooms with some melted dark chocolate. Alternatively, you can dip the bottom of the mushrooms into the chocolate, then dip into the sesame seeds.

Step 10

Store in an airtight container at room temperature for up to a week. If the meringue was properly prepared, the meringue mushrooms will stay crispy. The improperly prepared meringue will weep or become soggy.