To prepare the filling:
1. Melt the butter with the chopped onions in a pot on low heat without browning
2. Add the flour and combine, allow cooking on very low heat for a few minutes while stirring to cook the flour or else it will turn out sweet. When you see white spots appearing the flour will be cooked.
3. Heat the stock until it almost boils. Add the stock ladle by ladle to the butter flour mix ensuring it comes to boil with every ladle. The idea is to get a very thick sauce.

It should bubble like volcano lava.
4. Season to taste and let the sauce cook on very low heat for 1 to 2 minutes.
5. Add the Parmesan and the chopped parsley to the sauce and combine well, this works best with a wooden spoon or ladle.
6. Transfer the mixture to flat container and allow cooling
7. Cover the container with a piece of greased parchment paper to avoid skin forming on top

8. Leave to cool overnight in the fridge.
9. Form the next day small balls, about 20 grams each, from the mix and coat them first with flour, then whisked egg and lastly with bread crumbs

To complete the dish:
1. Deep fry the snack balls in 180 degree (350 F) oil for 2 to 3 minutes until golden and crisp, serve hot with mustard.