Pour the mixture into dessert glasses or ramekins and refrigerate for at least 4 hours, preferably overnight.
Prepare the fruit filling:
Wash the strawberries, remove the stems, and cut into small pieces. Wash and drain the blueberries.
Combine the strawberries, blueberries, sugar, and lemon juice in a bowl. Let the mixture rest for about 10–15 minutes to allow the fruit to release its juices.
Serve:
Remove the chilled panna cotta from the refrigerator and garnish with the strawberry and blueberry mixture.
If you don’t want to use gelatin, you can use agar-agar as a plant-based alternative. Follow the dosage instructions on the package.
Vary the fruit according to the season or taste