Preparation

1. Preheat oven to 225°F (107°C) and line a baking sheet with parchment paper.
2. Ensure your mixing bowl and beaters are clean and dry.

Whipping Egg Whites

1. Add egg whites to the mixing bowl and beat on medium speed until foamy.
2. Add a tiny splash of lemon juice or a pinch of cream of tartar.

Adding Sugar

1. With the mixer running, gradually add sugar one spoonful at a time until dissolved.
2. Increase the speed and whip until the meringue is glossy and holds firm peaks.

Final Preparations

1. Sprinkle in cornstarch and whip again until just mixed.
2. Pipe into circles on the prepared baking sheet, creating a wall and leaving a dip in the center.
3. Bake for 60 to 75 minutes, then turn off the oven and leave them to cool inside for at least 1 hour.

Making Lemon Curd

1. In a saucepan, whisk egg yolks and sugar until smooth.
2. Mix in lemon zest, lemon juice, and a pinch of salt.
3. Cook over low heat, whisking constantly until thick enough to coat the back of a spoon.
4. Remove from heat and stir in butter until melted and glossy.
5. If needed, strain the curd through a fine mesh strainer to remove any bits of cooked egg.

Assembling and Serving

1. Fill each cooled meringue nest with lemon curd.
2. Top with fresh berries and garnish with lemon zest or mint if desired.