Preheat the oven to 180C/350F/Gas 4.To make the caramelised pineapple, melt the butter for 2-3 minutes in an oven-proof saucepan. Add pineapple wedges, brown sugar and vanilla.
Place into the preheated oven for four minutes.
To make the sabayon, over a pan of simmering water place the sabayon ingredients into a bowl. Whisk constantly over medium heat until light and doubled in size, for 3-4 minutes.
Serve the caramelised pineapple with the sabayon sauce on the side.