Heat the oven to 200°C/400°F. Toss the butternut squash with a drizzle of olive oil on a baking sheet and place in the oven, roast for 30-40 minutes.
Place the chickpeas and baking soda in a saucepan and cook over a high heat for 3 minutes. Add the water and bring to a boil, cook for about 20 minutes until really tender. Drain them and place in a food processor, mix until you get a stiff paste. Add the roasted squash and mix again. With the machine still running add the tahini, lemon juice, garlic and salt then drizzle in the ice water and mix for another 5 minutes.
Transfer to a bowl and drizzle with olive oil before serving.
Nutrition information is an estimate and will vary depending on the ingredients used.