Cook the peas in the broth until tender, about 10 minutes, then purée smooth with an immersion blender or push through a sieve.
Make a light roux from the butter and the flour, stir it into the pea purée, and bring to a boil.
For the fried pea fritters, mix the egg smoothly with the milk and a pinch of salt to get a thick, pourable batter.
Heat plenty of oil or lard in a pan, drip the batter through the back of a grater into the oil in small drops, and fry golden, then drain on paper towel.
When serving, mix the egg yolk, the cream and the butter into the soup, don't boil it any further.
Sprinkle the fried pea fritters over the soup just before serving, so they stay crisp.
Based on: Malatinszky Fanny szakácskönyve (a classic Hungarian cookbook), modernised. Calories and protein are estimated.