Wash the rhubarb and cut into 1cm pieces.
Grease 2 ovenproof glasses with 1 tbsp oil and sprinkle with breadcrumbs. Grind or finely chop the hazelnuts.
Separate the eggs. In a bowl, mix the egg yolk with vanilla sugar, flour, hazelnuts, yogurt, baking powder and the remaining oil.
In a separate bowl, whisk the egg whites with a pinch of salt until stiff and then fold them into the yolk mixture.
Spoon the mixture into the glasses, so that each glass is half full. Top with the rhubarb pieces.
Bake in the preheated oven at 200°C (180°C fan, gas 6).