Put the pitted dates in a heatproof bowl. Pour over 150ml boiling water to cover. Leave to soak for 20 mins until softened, then tip into a blender with the water from the bowl, tahini, lemon juice, garlic clove, ground cumin and neutral-tasting oil. Blitz until smooth, adding more water if needed to make it drizzly. Season to taste. Will keep chilled in an airtight container for up to five days.