1 pound kielbasa sausage
2 tablespoons ketchup
1 (16 ounce) can chopped mushrooms
2 tablespoons chopped onion
Place kielbasa in large bowl and sprinkle with ketchup. Cover and refrigerate for two hours, under refrigeration.
Slice mushrooms into 1/2 inch slices. Place mushrooms in another large bowl and pour ketchup over. Cover and refrigerate overnight.
While the mushrooms are chilling, place onions in a medium saucepan and bring to a boil in a small saucepan. Remove mushrooms from skillet, pieces both cooked and uncooked, and place in small bowl. Cover and allow to cool. Drain liquid, reserving 1/2 cup to stay warm.
In a small bowl, mix ketchup, mushrooms, onion and flour and stir into kielbasa mixture. Pour over mushroom mixture and toss well. Cover and refrigerate about 8 hours, stirring often.
Pour 1/2 cup of the ketchup mixture into a large bowl and stir in remaining 1/2 cup ketchup mixture. Bring to a boil while stirring. Add mushrooms and onions and cook for about 5 minutes. Add mushrooms and onions to kielbasa mixture and toss well. Stir sauce up until smooth.