Preheat your oven to 225°F (110°C). Line two baking sheets with parchment paper. Ensure your mixing bowl and whisk attachment are impeccably clean and free of any grease, as this is crucial for meringue stability.

In the clean bowl of your stand mixer, combine the egg whites and a pinch of salt. Beat on medium speed until soft peaks form. This means when you lift the beaters, the egg whites hold a soft shape but droop over.

Gradually add the superfine sugar, about a tablespoon at a time, while the mixer is still running on medium-high speed. Continue beating until the sugar is fully dissolved and the meringue is stiff, glossy, and holds firm peaks. To test if the sugar is dissolved, rub a small amount of meringue between your fingers; it should feel smooth, not gritty.

Gently fold in the vanilla extract and cream of tartar using a spatula. Be careful not to overmix, as this can deflate the meringue.

Transfer the meringue to a piping bag fitted with a star tip. Pipe small kisses onto the prepared baking sheets, leaving a little space between each one.

Bake for 60-75 minutes, or until the meringues are dry to the touch and lift easily off the parchment paper. They should be crisp on the outside and slightly chewy or marshmallowy on the inside. Turn off the oven and let the meringues cool completely inside the oven with the door slightly ajar. This slow cooling prevents cracking.