For the green curry paste, place all of the paste ingredients into a mortar and pound with a pestle until they form a paste. (You will not need all of the paste; store unused portion in a tightly covered jar in the fridge for up to two weeks.).
For the skewers, mix three tablespoons of the green curry paste together with one tablespoon of the groundnut oil until well combined.
Cut the tofu and aubergine into 1.25cm/½ inch cubes and thread onto the wooden skewers, alternating the tofu and aubergine along the skewer. Lay the skewers flat on a plate and pour over the curry paste mixture to coat well, rubbing the aubergine and tofu all over. Cover with cling film and leave to marinate for at least 30 minutes, or overnight if possible, in the fridge.
Preheat the grill to medium.
Brush the vegetables with the remaining groundnut oil and cook under the grill for 8-10 minutes, turning once, or until the skewers are golden-brown all over. Set aside.
For the satay sauce, heat the oil in a small pan and fry the shallot, garlic, chillies and spices for 4-5 minutes, or until the shallot and garlic are softened.
Mix the peanut butter with a little warm water to make a thinner paste and add to the pan, followed by the coconut milk. Bring to the boil, then simmer for 6-8 minutes, or until the sauce thickens. Season, to taste, with lime juice and salt. Divide the sauce equally among four smalll bowls.
Serve the skewers on individual plates with a small bowl of satay sauce on the side.