Follow these steps to create your very own Mexican Chocolate Milk Cake:

1. Preheat Your Oven: Begin by preheating your oven to 350°F (175°C). Prepare two 9-inch round cake pans by greasing and lightly flouring them.
2. Mix Dry Ingredients: In a large mixing bowl, combine flour, sugar, cocoa powder, baking powder, baking soda, salt, and cinnamon. Whisk them together until well combined.
3. Mix Wet Ingredients: In another bowl, combine milk, vegetable oil, eggs, and vanilla. Whisk these together until the mixture is smooth.
4. Combine Mixtures: Gradually add the wet ingredients to the dry ingredients, mixing on low speed until combined. Be careful not to overmix.
5. Add Water: Slowly incorporate hot water into the batter. This step makes the batter thinner but will result in a moist cake.
6. Optionally Add Chocolate Chips: If desired, fold in chocolate chips to enhance the richness of the cake.
7. Pour Batter: Divide the batter evenly between the two prepared cake pans.
8. Bake: Place the pans in the preheated oven and bake for 40-50 minutes, or until a toothpick inserted into the center comes out clean.
9. Cool Cakes: Remove the cakes from the oven and let them cool in their pans for 10 minutes. After that, transfer them to a wire rack to cool completely.
10. Prepare the Frosting: While the cakes cool, beat heavy cream, powdered sugar, and vanilla extract together in a bowl until stiff peaks form.
11. Assemble: Once the cakes are completely cool, spread frosting on the top of one layer, place the other layer on top, and cover the entire cake with the remaining frosting.
12. Garnish: You may wish to decorate the top with additional chocolate shavings, a sprinkle of cinnamon, or any other chosen topping.

Following these simple steps will lead you to a beautiful and delicious Mexican Chocolate Milk Cake!