Add the spinach in batches to a large hot frying pan and stir constantly for about 2 minutes. As each batch wilts, remove and place in a strainer, squeezing out the excess water with the back of a spoon.

Melt the butter in a pan. Add the onion and garlic and cook over low heat for about 8 minutes, or until soft. Add the spinach, salt and pepper and cook for 1 minute. Add the cream, simmer, and cook for about 2 minutes. Stir in the lemon juice.

In a blender or food processor, blend the mixture until fine and well combined. Check the seasoning, then serve.