Brown the duck breast in a big and deep frying pan on high temperature
Fry the onions, carrots, parsnip and celeriac in a pan and add to the duck breast
Add water, chicken broth cube, bay leaves, peppercorns, apple vinegar and thyme to the pan and bring to a boil
When it has been boiling for a few minutes, put the temperature down and let it simmer for 3 hours with lid on pan
Remove lid, fish all ingredients out of the pan with a skimmer
Reduce the stock at good heat until you have about 2-3 dl left, it can take 30 minutes
Strain the stock in a bowl and put in fridge until you need it
Put 2 big tablespoons of butter in a frying pan with thick bottom
Let the butter melt and bubble on medium heat
Add 2 tablespoons of flour and mix well until well combined
Keep stirring while it bakes until it's light brown in colour, it should not be too dark!
Add the duck stock while stirring
Add the cream, while stirring
Bring to taste with salt, pepper (and currant jelly if you like)