1. Preheat oven to 225°F (110°C). Line two baking sheets with parchment paper and trace three 7-inch circles on each sheet.

2. In a stand mixer, beat egg whites and salt on medium speed until foamy (1-2 minutes). Gradually add sugar one tablespoon at a time while beating continuously.

3. Increase speed to high and beat for 8-10 minutes until stiff, glossy peaks form and mixture feels smooth with no sugar grains.

4. Add vinegar, cornstarch, and vanilla in the final minute of beating until fully incorporated.

5. Divide meringue into six equal portions. Spread each portion within traced circles, creating 1/2-inch thick disks with slightly raised edges.

6. Bake for 60-75 minutes until meringues are dry to the touch and lift easily from parchment. Turn off oven, crack door open, and let cool completely inside for 2+ hours.

7. Prepare berries: Combine all berries with sugar and orange zest. Let macerate for 20-30 minutes.

8. Make whipped cream: Beat cold heavy cream, powdered sugar, and vanilla until stiff peaks form (3-4 minutes). Fold in mascarpone if using.

9. Assemble trifle: In a large glass trifle bowl, layer meringue pieces (broken to fit), whipped cream, and macerated berries. Repeat until all six meringue layers are used.

10. Top with final dollop of cream, arrange whole berries, scatter pomegranate arils, add mint leaves, and dust with powdered sugar. Refrigerate up to 2 hours before serving.