Soak cranberries in slightly warmed apple juice for at least 2 hours. Mix millet flakes with oat flakes. Heat apple syrup with walnut puree and stir until smooth. Mix with the flakes and knead well.
Grease a rectangular silicone mold (25 x 25 cm) with oil. Spread the mixture in the mold and press with your hands until nice and even.
Spread the drained cranberries on one half of the mixture, cover with the other half of the granola bar mixture and press down a little. Now place the pan on the lowest rack in the oven and bake at 160 degrees hot air for about 30 to 40 minutes.
When the surface is lightly browned, turn off the oven, open the oven door and let the mixture cool completely.
Brush the cold mixture with melted chocolate and sprinkle with the apple syrup. When the chocolate has set, divide into bars with a sharp knife.