One of many versions of the Hungarian vegetable dish. It is often used to compliment meat dishes, and has the texture of a 'thick soup'.
Melt the butter in a saucepan, then stir add onion. Cook until beginning to turn translucent.
Add peas, stirring gently to incorporate. Let cook briefly to warm.
Add salt, pepper, parsley, and enough water to cover the peas. Continue simmering.
Mix together the milk with flower in a small dish. Add some of the juice from the főzelék to temper, then mix back into the peas.
Continue cooking briefly to thicken.