Cut the onion into small pieces. Melt the butter on low heat and add the onions. When the onions are slightly translucent, the flour can be added. Let the roux lightly brown and add the cold water. Bring to the boil and season with salt. When it`s salty enough, add a good helping of ketchup. Season with a little sugar and the sauce is ready.
In the meantime, cook the pasta.
For the hunter schnitzel, cut the hunting sausage into slices. Beat the eggs in a deep plate with a dash of cream and add the breadcrumbs to a second plate.
Now turn the slices of hunting sausage first in the egg-cream mixture, then in the breadcrumbs. When all the slices are breaded, they can be fried in oil in a pan.
A note: do not season the Jagdwurst under any circumstances, as it is salty by itself.