The phrase "topping mixture" refers to a combination of ingredients that is used to cover or sprinkle on top of a dish or dessert to enhance its flavor or appearance. Full definition
Top the mixture with mozzarella cheese and put a lid on the skillet only for few minutes to melt the cheese. (primaverakitchen.com)
Using your hands, sprinkle all of topping mixture over fruit mixture. (bostonmamas.com)
Remove the cheesecake pan from the freezer and transfer the cooled off chocolate topping mixture on top of the peanut butter center, spreading it evenly. (thehealthyfamilyandhome.com)