Heat the oven to 200C/fan 180C/gas 6. Halve the peaches, then twist the halves to separate them and flick out the stone. Put the peaches cut-side up in a baking dish. Mix the sugar and butter together and then add the bourbon. Spread this over the cut side of the peaches and into the dip left by the stone.
Put 3 tbsp water into the base of the dish and bake the peaches for 30-40 minutes. They should be cooked through and on the point of collapse, but still hold their shape. Serve with the vanilla ice cream and an extra sprinkle of bourbon if you like.