Roast the pumpkin with the tablespoon of olive oil and the garlic clove 30-40 minutes, until tender. Cool (this step can be done a day or two beforehand).
Place the chickpeas in a small saucepan and add a splash of water. Cook gently for a few minutes until the chickpeas are heated through.
Place the chickpeas together with a dsp cooking water - keeping any leftover cooking water - the pumpkin, garlic, ground cumin and olive oil in a blender and blitz until smooth, adding a little more of the cooking water if the mixture is too dry.