Add the chicken stock to a pan and bring to a simmer. Add a good pinch of salt then add the chopped green beans and simmer until cooked but still firm to the bite.
Meanwhile, melt the butter or zsír in a separate pan, then add the flour. Stir continoulsy until a roux forms, then cook the roux of 1-2 minutes .
Add the garlic and cook for 1 minute, then take the pan off the heat and stir in the sweet Hungarian paprika.
Return the pan to the heat then add the sour cream and water gradually, stirring continuously with a whisk to avoid lumps forming.
Add the resulting sauce and the chopped parsley to the green beans and mix well. Bring the beans and sauce to a simmer and cook for for 4-5 minutes. Add some more chicken stock or water if the sauce thickens too much.
Season to taste then serve.