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. Gradually add caster sugar, a tablespoon at a time, whisking until stiff, glossy peaks form and sugar is dissolved.
03 - Gently fold in cornstarch, vinegar, and vanilla extract until fully combined.
04 - Spoon or pipe small mounds about golf ball size onto the prepared baking tray, spacing them well apart.
05 - Bake for 1 hour until crisp outside. Turn off oven and let meringues cool inside with door ajar.
06 - Combine raspberries, sugar, and lemon juice in a small saucepan. Cook over medium heat for 5–7 minutes, stirring constantly, until raspberries break down. Press through a fine sieve to remove seeds. Refrigerate until chilled.
07 - Whisk heavy cream, powdered sugar, and vanilla extract until soft peaks form.
08 - Once meringues are completely cool, carefully cut a small cavity in the base of each. Fill with whipped cream using a 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.