Preparation time: 10 minutes (+chilling)
Cooking time: nil
Makes 16 wedges
This slice will keep, covered with plastic wrap, in the refrigerator for up to 2 weeks.
Put the oats, walnuts, coconut, chia seeds, cinnamon, cocoa and vanilla in a food processor and process until all the ingredients are finely chopped.
With the motor running, start adding the dates, a few pieces at a time, processing until all the dates have been added and the mixture is starting to come together. Use clean hands to bring it together completely, adding 1-2 teaspoons of cold water if necessary.
Press the mixture evenly into a round 20 cm (8 inch) cake tin, smoothing the surface firmly with the back of a metal spoon. Cover and refrigerate until ready to serve.
To serve, dust with icing sugar and cut into thin wedges.