Dice the onions and bacon and sauté in the butter on a medium heat. Cut the mushrooms into slices and slightly larger pieces. Add the tomato paste or ketchup and simmer for about 5 minutes. Add the flour, stir and let simmer for about 2 minutes.
Deglaze with the white wine. Add the cream and the beef broth and simmer for another 10 minutes, seasoning with salt and pepper in between.