Drain the chickpeas and beans, then rinse under fresh water, transfer to a food processor and pulse briefly (20 sec or until the beans and peas are roughly chopped). Add the onion, garlic, herbs (keeping a small amount for garnishing), baking powder, 1 tbsp of Berbere (saving the rest for later) and a large pinch of salt. Pulse in intervals of roughly 20 seconds, scraping down the sides each time, continue until you have a consistent, coarse paste.
Add the water and process until it just comes together. Using two spoons, form the paste into balls or quenelles and place on a tray. If the first ball does not hold its shape and crumbles at all, return to food processor and add a little more water. Refrigerate for 15 minutes.
Meanwhile, combine the yoghurt, tahini, lemon juice, cumin, and remaining 1 teaspoon of Berbere with a pinch of salt until smooth. Pour into a serving dish and top with remaining chopped herbs.
In a large, heavy based pan, heat to 180ºC enough canola oil to shallow-fry the falafels in batches until golden brown on all sides. Drain on kitchen paper and sprinkle with a little salt.