Line the troughs of a muffin baking tray (twelve troughs) with one paper baking tin each. Preheat the oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Coarsely crumble the cinnamon flakes with your hands.
Mix about 60 g flakes, flour, baking soda, 1 pinch of salt, vanilla sugar and 100 g sugar. Stir oil, eggs and 250 g sour cream until smooth. Peel apples and grate roughly around the core. Add to the egg and oil mixture.
Quickly stir into the flour mix (there may still be small lumps of flour in the dough).
Spread the dough into the moulds. Bake in a hot oven for about 20 minutes. Take out and let cool down.
To serve, whisk 150 g of sour cream and 75 g of sugar with the whisks of the mixer until creamy. Decorate muffins with sour cream and the rest of the cinnamon flakes.