Whisk Together The Beef Stock, Heavy Cream, Flour, Soy Sauce, Black Pepper, And Rosemary In A Large Saucepan Until Smooth. Cook And Stir Over Low Heat Until Thickened, About 10 Minutes, Stirring Occasionally. Stir In The Meatballs, And Continue Cooking Until Meatballs Are Heated Through, About 5 More Minutes.