Preheat oven to 110° C / 230° F.

Line a baking tray with parchment or a silicone baking mat. Fit a piping bag with a 5/16-inch round piping tip, and set aside until ready to use.

Add egg whites to a large mixing bowl or the bowl of a stand mixer. Whip on medium-high until soft peaks form.

Gradually add sugar, continuing to whip on medium-high speed until meringue is thick and glossy, and stiff peaks form.

Add the vanilla extract and the mint green food coloring.

With a rubber spatula, scoop meringue mixture into a piping bag fitted with a 1/4-inch to 1/2-inch round tip.

Pipe onto prepared tray.

Sprinkle with nonpareils, if using.

Bake in preheated oven for one hour. Without opening the door, turn off the oven and allow cookies to cool in oven for 1 – 1 1/2 hours more.

Serve immediately. Store leftover meringue cookies in an airtight container at room temperature for up to one week.