Beat butter and sugar at medium speed with an electric mixer until light and fluffy.
Add vanilla and add eggs, one at a time, beating until blended after each addition.
In a blender or food processor place cereal and blend into a fine powder and set aside.
In a medium bowl combine cereal, flour, cocoa powder, coffee, baking soda, salt, and Mexican chocolate.
Gradually add dry mixture to butter mixture, beating until blended.
Drop dough by heaping tablespoons, 2-inches apart onto parchment paper-lined baking sheet. Dropping identical rounded dough balls ensures your cookies feature a uniform shape.
Bake for 12 to 14 minutes or until set.
Cool on baking sheet for 2 minutes. Transfer cookies to wire rack, and cool completely about 20 minutes.