Preheat the oven to 200°C/fan 180°C/gas mark 4. Toss the pumpkin pieces in 1 tbsp oil with some seasoning and lie on a wide roasting tray. Carefully take a small slice off the top of the bulb or garlic so that you expose the tops of each clove, making sure not to slice the bottom part, which will hold it together. Drizzle this with 1 tsp olive oil and wrap with tin foil.
Place the pumpkin and garlic in the oven for 40-45 minutes, turning halfway through, until the pumpkin is cooked through. Check the garlic by piercing a clove with a knife – if it is still hard, place it back in the oven for another 15 minutes until soft.
Once the garlic is cooked through, leave to cool slightly then squeeze it out of its skin. Place this in a food processor with the roasted pumpkin, chickpeas, lemon juice, remaining olive oil, tahini and some seasoning. Blitz until smooth, adding a splash of water if it needs loosening. Transfer to a bowl and garnish with the chopped pumpkin seeds.