Begin with the outside of the log. Place the dates in a food processor. Add a little water, just enough to cover the dates. Add the oats and blend until smooth. It should form a hard coherent dough that you will be able to spread out. If the dough is too sticky, you can add 1-2 tbsp of ground flax seeds.
Transfer the dough on a plastic wrap (or a beeswax wrap). Spread it to make a rectangle about 30 cm x 45 cm (a bit less than 1 cm thick).
For the inside, add the reminding ingredients into the food processor (walnuts, cocoa powder, maple syrup, vanilla extract) and blend until creamy.
Spread the mixture on top of the dough.
Roll the dough on the long side to form your log. At this point you should have a log, 30cm long, with a spiral made of chocolate in the middle.
Roll the wrap around the log and close at both ends. Using your hands, shape the dough to make a nice cylinder. Make everything smooth and uniform. Let it harden in the fridge overnight and enjoy the next day!