Allow the peas to thaw.
Peel and finely dice the onions.
Melt the butter in a pan and fry the onion until slightly softened. Mix in the peas, cover with stock and bring to the boil.
Reduce the heat and simmer for 10 minutes until the peas are cooked.
Pour in the cream and blitz with a hand blender until smooth.
Add a little more stock if needed and season with salt and pepper.
Wash the parsley, shake dry and finely slice the leaves. Serve the soup in bowls topped with a grinding of pepper and the chopped parsley.