Mix together the wasabi powder and water to make a paste. Line a baking tray (sheet) with a non-stick baking mat. Put the cream and invert sugar in a saucepan and bring to the boil. Take off the heat and leave to cool until it reaches 65-70°C (149-158°F). Blend a small amount of the cream with the wasabi paste and mix to a loose paste. Add it back to the cream and mix we