01 - Preheat oven to 230°F and line a baking tray with parchment paper.
02 - In a clean bowl, whisk egg whites until soft peaks form. Gradually add caster sugar one tablespoon at a time, whisking continuously until stiff, glossy peaks form and sugar is completely dissolved.
03 - Gently fold cornstarch, vinegar, and vanilla extract into the meringue mixture until just combined.
04 - Spoon or pipe small mounds approximately golf ball-sized onto the prepared baking tray, spacing well apart to allow for even air circulation.
05 - Bake for 1 hour until crisp and dry to the touch. Turn off oven and leave meringues to cool completely inside with door slightly ajar to prevent cracking.
06 - Combine raspberries, sugar, and lemon juice in a small saucepan. Cook over medium heat for 5-7 minutes, stirring occasionally, until raspberries completely break down. Press through a fine sieve to remove seeds. Refrigerate until chilled.
07 - Whisk heavy cream, powdered sugar, and vanilla extract together until soft peaks form and cream holds its shape.
08 - Once meringues are completely cool, carefully cut a small cavity in the base of each. Fill each cavity with whipped cream using a small spoon or piping bag.
09 - Drizzle generously with chilled raspberry coulis. Garnish with fresh raspberries and mint leaves if desired. Serve immediately for optimal texture contrast.