Add the milk and cinnamon sticks to a medium pot and cook over medium heat until it reaches a gentle simmer, stirring occasionally. The milk will start to gently steam, and small frothy bubbles will form on the edges.
While the milk reaches a simmer, blend the Marías cookies and evaporated milk in a blender until completely smooth.
Once the milk reaches a gentle simmer, slowly pour the blended cookie mixture into the milk, stirring to combine.
Add the piloncillo and continuously stir for 10 minutes to melt the piloncillo and thicken the atole. The atole should evenly coat the back of your stirring spoon.
Once it has reached the proper consistency, discard the cinnamon stick.
Serve immediately in mugs and dust with ground cinnamon if desired.
Notes
If you don't have piloncillo, substitute ½ cup brown sugar.
Piloncillo usually comes in 8 ounce cones. To break apart, microwave piloncillo in a bowl in 15 second increments to soften the cone and break apart for your desired amount.
You can adjust the thickness of the atole to your liking. To make it less thick, add milk 1 cup at a time until it reaches your desired consistency.