For the tahini dressing
Preheat oven to 220°C, gas mark 7. Place the butternut or pumpkin wedges on a large baking sheet with the olive oil, seasoning, chickpeas and cumin. Toss to coat and roast for 25-30 minutes or until golden and caramelised. Add the walnuts to the tray with 5 minutes of cooking time left so they can toast. Remove from the heat and allow to cool slightly.
To make the dressing, place the tahini, olive oil, lemon juice and seasoning in a small bowl and whisk to combine. Gradually add the warm water, a little at a time, to form a smooth dressing.
Arrange the pumpkin on a platter with the chickpeas and walnuts then top with the mint, parsley and drizzle over the dressing.