Wash and peel the apples, halve them and remove the core with a corer. Preheat the oven to 200°C (convection oven). Then place one apple half with the cut surface downwards on a chopping board. Put a wooden stick (or alternatively a wooden ladle) to the left and to the right of the apple. Then cut the whole surface of the apple every 2 mm but make sure you don’t cut through completely. The wooden sticks should, in fact, stop the knife so that you can’t cut through completely. Repeat with the remaining apple halves.

Melt butter in a small bowl and brush a baking dish with a little melted butter. Place the apples in the buttered baking dish. Add sugar and cinnamon powder to the remaining melted butter. Brush the entire surface of the apples with the mix of melted butter and sugar (part of the mix will be needed later). Cover the baking dish with aluminum foil and bake in the oven at 200°C for 20 minutes.

In the meantime, coarsely chop the walnuts and add them to the remaining butter and sugar together with oat flakes and flour. Mix well. Take the apples out of the oven after 20 minutes, remove the aluminum foil and distribute the mix of walnuts and oat flakes on the apples.

Bake in the oven (without aluminum foil) for another 15 minutes until the apples are soft (skewer with a fork). Serve the Hasselback apples with walnut crumble hot or cold. They taste excellent with a scoop of ice cream or whipped cream.