Fill sous vide water bath with water and set sous vide to 180F.
In a small saucepan, heat the water and sugar, stirring often. Once the sugar has dissolved, remove from heat and cool. Stir in the cognac or brandy and set the syrup aside.
Place peach halves in a food safe vacuum bag. Pour in the syrup. Vacuum seal, being careful the syrup does not get sucked out with the vacuum sealer.
Place the peaches in the water bath and cook for 30-40 minutes.
Remove from the water bath and immediately place in an ice bath to stop the peaches from continuing to cook.
Peel the skin off the peaches just prior to serving.
Serve the peaches on their own, with creme anglaise, or with vanilla ice cream.