Preheat the oven to 225°F. Line a large baking sheet with parchment paper.

Add the egg whites to the bowl of a stand mixer. Using the wire whisk attachment, beat at high speed until the eggs are foamy and soft peaks are just starting to form, about two minutes.

With the mixer still running, slowly add the sugar, 1 tablespoon at a time, until all of it is added. Do not stop the mixer to scrape any sugar that might be on the sides of the bowl. Continue to beat until mixture is thick, glossy and stiff peaks form. Once the peaks form, you can scrape the sides of the bowl to get any sugar that stuck to the sides, add it back into the mixture and then beat on high for a few more seconds until that excess sugar is incorporated. I found that it is important not to stop the mixer in between. If you stop it, the mixture does not whip up to stiff peaks.

Transfer the meringue to a large piping bag with an open star tip. I used a Wilton 4B tip which has a front opening of about .5 inch. You can use other tips or tip sizes.

Pipe the meringue into ovals between 1.5 inches and 2 inches long onto the prepared baking sheet. Try to make the meringues all about the same size. The cookies can be piped pretty close together as they do not spread much. To pipe, make it like you are drawing an oval and then add another partial layer on top to close up the oval so there is no hole in the middle. See photo in post for reference.

Wet your finger and press down on the tops to remove the points on the cookies. If using sprinkles, sprinkle the tops with sprinkles.

Place cookies into the oven and bake for 1 hour. Without opening the oven door, turn off the oven and keep the cookies inside the oven for an additional one hour. Be careful to only keep them in the oven for one extra hour. If you leave them too long, they will fully dry out inside. When the cookies are done, they will be lightly tanned/off-white in color. They should feel dry on the outside and you should be able to pull them off the parchment paper easily. The cookies will initially be very crisp when they are done but if you let them sit out a few hours uncovered at room temperature, the inside will become soft and chewy (but the outside stays firm and should not turn sticky). Once they reach this stage, they can be stored in an airtight container.