Run a small, sharp knife round the top of the aubergine, 1cm/½in or so below the stalk and only just cutting through the skin; then make four evenly spaced, similarly shallow cuts, along the length of the aubergine right down to the end.
Grill the aubergines for about 20 minutes, turning every 5-7 minutes or so, until evenly cooked with charred skin, and until the aubergine feels soft, but not too collapsed within. In the case of the purple aubergines, the skin will also have turned a dull brown colour. Transfer to a large, oval, white plate and allow to cool for two minutes.
Peel away the aubergine skin in four long, narrow sheets using a small knife. Without cutting right through the stalk end, cut the aubergines in half lengthways and gently prise apart until you have two horizontal halves remaining attached at the top end
Mix the garlic and parsley with the olive oil until well combined and spoon the mixture over the aubergine. Season lightly with salt (not too much - the cheese is salty anyway) and pepper, and crumble the feta cheese over the top. If liked, trickle over more olive oil to finish.
Serve warm, or at room temperature with lemon squeezed over.