To make the seeded oatmeal cookies, bring butter to a foamy boil in a small saucepan. Place rolled oats in a suitable bowl and stir in the hot butter.
Combine flour, cornstarch and baking powder and sift over the top. Stir in sugar, vanilla sugar, 1 pinch salt, cinnamon and lemon zest. Mix with eggs and milk to form a dough. Stir in flaked almonds and walnuts.
Scoop out small heaps of the mixture and place them about 4 cm apart on baking trays lined with baking paper. Bake in a heated oven (175 degrees / convection oven: 150 degrees / gas: level 2) for about 25 minutes until light brown. Allow the crispy oat cookies to cool.