According to my mom’s recipe
300 to 400 g of chicken fillet (thigh or breast)
4 tablespoons of flour
Black pepper and salt
60 g butter
1 carrot, a slice of celeriac and parsnip, onion (dried or fresh) for the broth
Rinse the chicken fillet and put it in a deep saucepan. Cover with cold water and bring to a boil. Skim off the floating scum with a skimmer. Salt to taste and dip in a few peppercorns. For a more fragrant broth, you can dip in some vegetables such as carrot, celeriac, parsnip and onion (mom didn’t use any). When the meat is well cooked through (allow about 60 minutes), prick it out of the broth and shred into pieces or more likely threads (use 2 forks or your fingers).
Melt the butter in another saucepan and stir in the flour. Cook until it browns a bit and begins to smell nice. While stirring vigorously, pour in ladle by ladle the hot (filtered) broth. Add a new ladle only when the porridge has absorbed the previous one. Dilute the porridge to taste (more liquid or thicker). Mind that it thickens as it cools and it thickens even more the next day.
Return the chicken threads to the porridge. Then season with freshly ground black pepper. Simmer for another 5 to 10 minutes, stirring constantly.
Serve the porridge hot, although I find it tastier at room temperature.
The same recipe can be used to make mushroom porridge (instead of chicken).