In a large saucepan with a lid, cook the stew, covered, over medium-low, stirring once, until heated through, about 5 minutes. In a bowl, mix the sour cream and horseradish; season. Bring a large pot of water to a boil. Season with salt, add the noodles and cook to al dente. Drain the noodles and return them to the pot. Stir in the butter and 1 tbsp. marjoram; season with salt and pepper. Divide the buttered noodles among plates, then top with the stew, horseradish cream and the remaining chopped marjoram.