1 tablespoon (15 grams) crème de menthe (optional)
1⁄2 teaspoon (2 grams) mint extract, or more if desired
1⁄2 teaspoon (2 grams) vanilla extract
Instructions
In the bowl of a stand mixer, stir together egg whites, sugar, and salt by hand. Place bowl over a saucepan of simmering water, being careful not to let water touch bottom of bowl. Cook, stirring with a rubber spatula until sugar is completely dissolved and a candy thermometer registers 160°F (71°C), 4 to 5 minutes. (While stirring, be sure to scrape sides of bowl with spatula—this will ensure no sugar grains are lurking on sides and will also help prevent egg whites from cooking.)
Carefully return bowl to stand mixer. Using the whisk attachment, beat mixture at medium-high speed until glossy stiff peaks form and bowl cools to room temperature, 8 to 10 minutes. Add crème de menthe (if using) and extracts, beating until combined. Use immediately.
Recipe by Bake from Scratch at https://bakefromscratch.com/hot-chocolate-sandwich-cookies/