01 - Preheat oven to 230°F and line baking tray with parchment paper.
02 - In clean bowl, whisk egg whites until soft peaks form. Gradually add caster sugar one tablespoon at time, whisking until stiff glossy peaks form and sugar dissolves completely.
03 - Gently fold cornstarch, vinegar, and vanilla extract into meringue mixture.
04 - Spoon or pipe small mounds, approximately golf ball size, onto prepared baking tray. Space well apart for even cooking.
05 - Bake for 1 hour until crisp outside. Turn off oven and let meringues cool inside with door slightly ajar to prevent cracking.
06 - Combine raspberries, sugar, and lemon juice in small saucepan. Cook over medium heat 5-7 minutes, stirring occasionally, until raspberries break down completely.
07 - Press raspberry mixture through fine sieve to remove seeds. Refrigerate until chilled and ready to serve.
08 - Whisk heavy cream, powdered sugar, and vanilla extract together until soft peaks form. Do not overwhip.
09 - Once meringues are completely cool, carefully cut small cavity in base of each bomb. Fill cavity with prepared whipped cream.
10 - Drizzle generously with chilled raspberry coulis. Garnish with fresh raspberries and mint leaves if desired. Serve immediately for optimal texture.