Beef stir fry sauce recipes. They vary in size. You can half or double, as needed. In all cases, simply combine the ingredients and add to your stir fry sauce. Thicken as necessary with the thickening mixture below.Sauce Thickening Mixture: stir together 2 Tbsp. cornstarch with 2 Tbsp. water until smooth. Add a to your simmering sauce at the end, adding a bit at a time, until it thickens as desired.