The falafel balls. Add chickpeas, onion, garlic, parsley, and cilantro in a food processor. Pulse for 30-40 seconds until it is finely chopped and holds itself together, but is not pasty. Add the spices, baking powder, flour, salt and water. Mix with hands until the mixture is smooth. Cover and leave it in the fridge for at least 1 hour.
Heat about 2 ½ inches (6 cm) of oil in a medium saucepan over medium-high heat to 350°F (180°C).
With wet hands, form a patty or a ball using 1 tablespoon of the mixture. Sprinkle the balls with sesame seeds and fry them in batches for about 4 minutes or until well browned. Remove from oil and drain on paper towels.
The tahini sauce. Before starting, stir the tahini paste in its tub. Put the paste into a mixing bowl and add the water, garlic, lemon juice, and salt. Stir until you get a thick sauce. Store in a jar in the fridge for up to a week. Before using add a little water to loosen, if needed.