Which ingredient is common to both the Hot Cinnamon Dulce and the Hot Horchata recipes?

The correct ingredient that is common to both the Hot Cinnamon Dulce and the Hot Horchata recipes is espresso. Espresso serves as the foundational base for both drinks, providing a rich, concentrated coffee flavor that enhances the overall profile of each beverage.

In the context of specialty coffee drinks, espresso is often the backbone that supports various flavor profiles and additions. In the Hot Cinnamon Dulce, the sweet and spicy notes come together with the espresso to create a balanced flavor experience. Similarly, in the Hot Horchata, the espresso combines with the creamy, sweet elements traditionally found in horchata to offer a unique twist.

While other ingredients like cinnamon do feature prominently in these drinks, it's the espresso that is the common thread that ties them together, making it essential to their identity as coffee beverages.