Line 2 baking trays with baking paper. Wrap chickpeas in a clean tea towel or paper towel and gently rub until dry. Transfer to a bowl. Place sweet potato in a separate bowl. Add 2 teaspoons oil and 2 teaspoons harissa to each bowl. Toss well. Spread chickpeas over 1 prepared tray and sweet potato over the other prepared tray.
Bake trays in 200 °C preheated oven for 25 minutes or until sweet potato is tender. Remove trays from oven. Stir in pepitas through chickpeas and return to oven for 8-10 minutes until pepitas are lightly browned and chickpeas are crisp. Cool on trays.
Meanwhile, rinse quinoa in a sieve under cold running water. Transfer to a small saucepan. Add 1⅓ cups water. Bring to the boil. Reduce heat, cover and simmer for 15-20 minutes, until water has been absorbed. Remove lid and fluff with a fork.
To make dressing, whisk all ingredients with 2 tablespoons water in a small bowl until smooth.
Divide quinoa, cucumber, cabbage, sweet potato, chickpeas and pepitas among 4 wide, shallow bowls. Top each bowl with an avocado quarter. Drizzle with dressing. Sprinkle with extra harissa. Serve with lemon wedges