Halve, the vanilla pod and scrape out the seeds, then place in a large pan along with 350g of the berries, the sugar and lemon juice. Bring to the boil over a medium heat.
Simmer for 3 to 4 minutes, or until syrupy and the berries are soft but holding their shape. Set aside to cool.
In a large bowl, whisk the cream to form peaks, fold through the yogurt and swirl through a third of the syrup.
Layer the rest of the syrup and cream in dessert glasses, garnish with syrup and fresh berries.