Yam Zucchini And Chickpea Salad

Name: Yam, Zucchini, And Chickpea Salad
Ingredients: 2 yams or sweet potatoes, diced into 1-inch pieces; 1 zucchini, diced into 1-inch pieces; 1 can chickpeas, rinsed and drained; 2 garlic cloves; 3 sprigs parsley, leaves finely chopped; 2 scallions, thinly sliced on bias; olive oil; 1 tablespoon tahini; zest and juice of 1 lemon; salt and pepper; 1 tablespoon olive oil