1Put the chocolate and powdered sugar in the blender and secure the lid.
2CHOP for 20-30 seconds until chocolate is finely chopped, stopping to use the tamper occasionally to press ingredients into the blades if required.
3Pour the cream, water and liqueur (if using) into a small saucepan. Add the chocolate mixture. Stir with a metal spoon over low heat until the sauce is melted and smooth.
4Serve over your favorite dessert.
5Transfer any unused sauce to an airtight container and store in the refrigerator for up to 2 weeks.