01 - Preheat the oven to 230°F and line a baking tray with parchment paper.
02 - In a clean bowl, whisk the egg whites until soft peaks form.
03 - Gradually add caster sugar, one tablespoon at a time, whisking continuously until stiff, glossy peaks form and sugar is completely dissolved.
04 - Gently fold in cornstarch, vinegar, and vanilla extract until just combined.
05 - Spoon or pipe small mounds, approximately golf ball size, onto the prepared baking tray, leaving adequate space between each.
06 - Bake for 1 hour until the exterior is crisp. Turn off the oven and allow meringues to cool completely inside with the door slightly ajar.
07 - Combine raspberries, sugar, and lemon juice in a small saucepan. Cook over medium heat for 5–7 minutes, stirring frequently, until raspberries break down completely.
08 - Press the raspberry mixture through a fine sieve to remove seeds. Refrigerate until chilled.
09 - Whisk heavy cream, powdered sugar, and vanilla extract together until soft peaks form.
10 - Once meringues have cooled completely, carefully cut a small cavity in the base of each and fill with the prepared whipped cream.
11 - Drizzle generously with chilled raspberry coulis. Garnish with fresh raspberries and mint leaves if desired. Serve immediately for optimal texture.