Place the vitamin C powder in the juice-collection jug of a centrifugal juicer (the most common type available at appliance stores) and juice the unshelled snow peas and snow pea shells. Pass the juice through a fine sieve. Immediately pour the juice into a 6 litre (210 fl oz) capacity distillation flask, place in a rotary evaporator*, set the water bath temperature to 30°C (86°F) and the cooling temperature to −25°C (−13°F), set the rotation speed to 45 RPM and distil at full vacuum for 20 minutes (depending on the strength of the vacuum) or until the peas are glazed in the juice. Tip the peas into a bowl. Cover until needed but don’t leave for more than 5 minutes.