What additional ingredient is included in both the Strawberry Shake and the Chocolate Shake recipes?

The inclusion of milk in both the Strawberry Shake and the Chocolate Shake recipes is essential, as it serves as the base ingredient that contributes to the shakes' creamy texture and helps to blend the other ingredients smoothly. Milk is a fundamental component of shake recipes, enabling the desired consistency and flavor while enhancing the overall richness of the drink.

In contrast, the other options, such as cherry and whipped cream, are typically used as toppings or garnishes rather than as integral components of the shake base. Ice, while crucial for creating a cold beverage, does not define the flavor profiles of either shake type. Thus, milk stands out as the core ingredient that both shakes share, making it the key element in their preparation.