Make the Dressing: Place the tahini, water, olive oil, lemon juice, honey, harissa, garlic and salt and pepper into a food processor or blender and process until smooth.
In a large bowl, place the arugula, spinach, chickpeas, red onion and cucumbers. Drizzle over the dressing and toss to combine well.
Notes
How to Toast Sesame Seeds: Heat a dry skillet over medium heat. Add a couple of tablespoons of raw sesame seeds and cook stirring or shaking the pan occasionally, for 3 to 5 minutes until they start to turn a deeper golden brown and smell nutty. Watch carefully as sesame seeds go from toasted to burned fairly quickly. Take them from the heat as soon as you get them to the color you like, and remove them from the pan.