1. In a small bowl combine the masa harina and water until you have a smooth runny paste, set aside.
2. Place the quartered guavas, piloncillo, cinnamon and 1 cup of water in a saucepan. Simmer until the guavas are soft and break up easily. Remove from heat and allow to cool slightly.3. Pour the cooled, cooked mixture into a blender, then add half a cup cool water and blend until everything is well combined.
4. Use a fine sieve to strain the blender mixture back into the saucepan you cooked the ingredients in. Add the pinch of baking soda and cook until it begins to bubble and after a few minutes the bubbling will stop. Next carefully pour in the milk and under low heat simmer for 10 minutes.
5. Now back to the rehydrated masa harina, add another half cup of water to make it very runny and pour into the pot and mix until well combined. IMPORTANT to note that you may also strain the masa mix into the pot or add it to the blender when blending everything. I like to add it last so I can taste and adjust anything before thickening up.
6. Simmer atole until it thickens up to your desired consistency. Taste and if needed add more piloncillo before serving. Serve warm topped with grated piloncillo and ground Mexican cinnamon. Enjoy!