Mix the aubergine cubes and olive oil until well combined. Season with salt and freshly ground black pepper.
Heat a griddle pan over a medium heat and grill the aubergine pieces on all sides, or until cooked through.
Thread the aubergine pieces onto the skewers and brush with the melted butter. Keep warm.
For the sauce, heat the vegetable oil in a wok and stir-fry the peanuts until golden-brown. Allow to cool slightly then blend in a food processor until smooth.
Fry the shallot and garlic in the wok for a few seconds, then add the chilli powder, chilli, brown sugar, soy sauce and water. Bring the mixture to the boil.
Add the peanuts and simmer for 8-10 minutes, or until the sauce is thick. Add salt and lemon juice, to taste.
Serve the aubergine kebabs drizzled with the peanut sauce.