Wash the strawberries, remove the tails, cut in half, leaving 4 berries for decoration. Put the cut strawberries in a bowl, sprinkle with 1 tbsp sugar and mash with a fork.
In another clean bowl, beat the egg whites until tender. Gradually add the remaining white sugar and whisk the vanilla sugar well. Whisk until firm peaks.
Add yogurt and crushed strawberries to the resulting mass and gently! stir with a spatula.
Arrange the dessert in 4 bowls, top with whole strawberries.