Bloom the gelatin by sprinkling it over cold water in a small bowl and letting it sit for 5 minutes.

In a saucepan, combine heavy cream, whole milk, and sugar. Add the seeds of the vanilla bean and the bean pod.

Heat over medium, stirring occasionally, until it reaches a gentle simmer. Do not let it boil.

Remove from heat and let steep for 10 minutes, then remove the vanilla pod.

Add the bloomed gelatin to the hot cream mixture and stir until fully dissolved.

Strain the mixture through a fine-mesh sieve into a bowl to catch any undissolved bits.

Lightly oil serving dishes or ramekins to make unmolding easier.

Pour the mixture evenly into the prepared dishes, filling about three-quarters full.

Let cool to room temperature, then refrigerate for at least 4 hours, preferably overnight.

Combine mixed berries, sugar, and water in a saucepan and heat over medium, stirring occasionally.

Simmer for 8-10 minutes until the berries are soft and saucy, mashing gently as needed.

Add lemon juice and stir to brighten the flavor. For thicker sauce, mix cornstarch with a tablespoon of water and add to the mixture, cooking for 1 more minute.

Let cool completely before serving.

Run a thin knife around the edge of each panna cotta and dip the bottom of the dish in hot water for 5 seconds to loosen.

Place a plate over the dish and flip quickly. Tap gently if needed to release.

Spoon berry sauce around the panna cotta and garnish with fresh berries and mint leaves.

Dust with powdered sugar if desired and serve immediately.