Sweet Lasagna with Plums
Rinse, halve, and remove the seeds from the plums. Cut into small pieces. Melt the butter in a saucepan, whisk in the flour, and sauté briefly. Whisk in the milk, stirring constantly. Add the vanilla sugar, salt, and sugar. Simmer for 10 minutes, stirring occasionally. Remove from the heat, let cool, and stir in the yogurt.
Preheat the oven to 200°C (approximately 400°F). Grease a baking dish with the butter. Layer the lasagna noodles, plums, and sauce, repeating as necessary. Finish with a layer of the sauce. Bake for 40 minutes, or until golden brown.