Add mazapan, corn starch, cinnamon, and sugar in a blender.
Pour 2 cups of milk and blend at high from 15 to 30 seconds (the longer, the smoother the drink will be).
Pour the remaining milk in a medium pot and warm it over medium heat.
Add the mazapan mixture to the pot.
Cook over medium-low heat for about 15 minutes while stirring constantly or until you'll see the mixture has thicken enough to coat the back of a spoon.
Pour atole in cups and enjoy immediately, or allow it to cool down slightly and serve later.
Notes
Atole de mazapan has a runnier texture compared to other types of atoles, but if you want a more thicker consistency, just allow to cook 5 to 10 minutes more.
Always make sure to let atole to cool down properly before giving it to children.
Atole will develop a thick skin in the surface once cooled. To prevent this, stir from time to time while the drink is cooling.