Which ingredient is used in both Tall and Grande Double Chocolaty Chip Frappuccinos?

The ingredient that is used in both Tall and Grande Double Chocolaty Chip Frappuccinos is mocha sauce. Mocha sauce contributes to the rich chocolate flavor of the drink, which is central to the Double Chocolaty Chip Frappuccino's profile. This sauce adds depth and sweetness, enhancing the chocolate experience as it complements the chocolate chips and other components of the beverage.

The other ingredients, such as espresso and whipped cream, are not part of the Double Chocolaty Chip Frappuccino. This drink is actually a non-coffee option, which means it does not include espresso. Ground chocolate, while it may be present in other chocolate or mocha beverages, is not specifically highlighted as an ingredient in this frappuccino. Therefore, mocha sauce is the key ingredient that is consistently included regardless of the size, making it the correct choice.