Not sure, HC--it comes out of a tin. At a guess I'd say boil peas until they start to liquify and then add salt and green food colouring.
Heh - I googled it and this is what I found:
- Bring a shallow pot of lightly salted water to a boil over medium-high heat. Add frozen peas, and cook for 3 minutes, or until tender. Drainpeas, and transfer to a blender or large food processor. Add cream, butter, salt and pepper to peas, and process until blended, but still thick with small pieces of peas.
Actually doesn't sound half bad!