Place the egg whites (save the yolks for the curd) in the mixer bowl with the fancy whisk attachment.
Beat egg whites, on medium speed until quite foamy, not just slightly foamy. Think mostly foam. Add the pinch of salt and increase speed to medium-high.
Slowly begin to sprinkle in the sugar. Continue to beat eggs until they become thick, glossy and messy. The egg whites will be the consistency of melted marshmallow.
I tossed the lime juice and vanilla right into the mixer at the end.
When I did this the second time I used a spoon and made little dots of meringue on the sheet. Not pretty stars, but not a giant blob either so it worked for me. the dots can be close together on the tray.
Bake meringues for 2 hours, until firm and hardened.
Remove from the oven and allow to cool completely on the baking sheet before filling and sandwiching.
Heat pot over a medium-low heat and add butter. Whisk the mixture, everything I read online said to keep a spatula nearby to help you get into the corners of the pan so it didn’t burn but I didn’t really use mine.
Cook the curd until the butter is melted, and the mixture is the thick and gooey. I whisked constantly, at first it smelled like butter, then eggs, then more like citrus, if you want the smell story.
Remove the curd from the flame and immediately pour into the fine mesh strainer over the medium bowl. Press through the strainer, leaving any cooked egg bits in the strainer; I took a picture of what was left in my strainer so you could see what I mean.
Place curd in a container, with a piece of plastic wrap placed directly over (touching) the curd. Place in the fridge until completely cold.
Spread a dollop of curd on the meringue and top it with another meringue. This is a sandwich cookie, which is like eating two cookies, but it only counts as one, best trick ever!