In a casserole, mix water and sugar and cook at 245°F (118°C) (use a candy thermometer).
In a bowl, set egg yolks, add the zest of half a grated lemon and two split vanilla beans. Mix everything. Slowly pour boiling sugar over the mixture, while whisking. Continue until it cools down.
In a bowl, whisk whip cream an carefully add drained yogurt. Add everything to the preparation while mixing all carefully. Pour in a rectangular mold and set in the freezer for at least 6 hours.
In a casserole, cook wild blueberries, sugar and balsamic vinegar for 15 minutes at low heat and cool down at room temperature.
Unmould the parfait by quickly setting the mould under hot water before turning on a plate.
Slice 6 slices of ice parfait, set each in a plate and add a great spoon of balsamic blueberries.
Garnish with mint leaves (optional).