1. Preheat the oven to 180°C/Fan 160°C/Gas 4 and grease a large baking tray with the oil.
2. Place all the ingredients, except the chocolate chips, in a medium bowl, add a generous pinch of salt and blitz briefly with a stick blender or in a food processor to make a slightly sticky dough. You may need to add ½ tablespoon water, if the mixture is a bit crumbly. Alternatively, mix together by hand. Stir in the chocolate until well combined.
3. Roll the mixture into 20 small balls and place on the greased tray. Flatten each of them with a fork, until around 1cm thick. Bake in the oven for about 15 minutes, or until firm and turning deep golden brown around the edges.
4. Leave to cool on the tray for a few minutes, then transfer to a wire rack. Store excess cookies in an airtight container in the freezer.
COOK’S TIP: If you don’t have dark chocolate chips, use any dark chocolate – as long as it contains over 70% cocoa solids – and chop it into small pieces.
AIR-FRYER TIP: Preheat the air fryer to 160°C, if needed. Prepare and shape the cookies as Steps 2–4. Air fry (in batches) for 10 minutes, or until firm and turning deep golden brown around the edges.