01 -
Heat the oven to 200°F (95°C). Line two baking sheets with parchment paper and fit a piping bag with a large star tip if using.
02 -
Add egg whites and salt to a very clean bowl. Beat on medium-high speed until foamy, about 30-45 seconds.
03 -
Add the vinegar and cornstarch. Beat until soft peaks form and the meringue starts to hold gentle shape.
04 -
Add the sugar 1 tablespoon at a time while beating. Continue for 4-6 minutes, until the meringue is glossy and holds stiff peaks.
05 -
Beat in the Jello powder and vanilla for 20-30 seconds, just until evenly colored. If making multiple flavors, divide the plain meringue first and add less Jello to each bowl.
06 -
Pipe or spoon 1 to 1 1/2 inch mounds onto the prepared baking sheets. Space them about 1 inch apart.
07 -
Bake for 90 minutes. Turn off the oven without opening the door and let the cookies dry inside for at least 2 hours, or until crisp and cool.
08 -
Transfer fully cooled cookies to an airtight container. Store at room temperature in a dry place for up to 2 weeks.