Mix the hazelnuts with the sugar, cream, cornstarch and baking powder. Then add the egg yolks.
Beat the egg whites until stiff and fold in loosely with a whisk. Grease an ovenproof dish with butter and sprinkle with breadcrumbs. Pour the casserole into the mold. Bake in the preheated oven at 170 degrees for approx. 25 minutes.