Rinse the rice under running water until the water runs clear.
Add the rinsed rice, almonds, cinnamon stick, and 3 cups of water to a large bowl or pitcher. Cover and let it sit in the refrigerator for at least 8 hours, up to 24 hours.
While the mixture is soaking, make the strawberry puree. In a medium saucepan, add strawberries, water, and sugar.
Over medium-low heat, bring the strawberry mixture to a simmer and cook uncovered for 10 minutes. Remove from the heat and allow it to cool slightly, about 10 minutes.
Blend the strawberry mixture until smooth. Transfer to an airtight container and set aside to fully cool, about 20 minutes, before transferring to the refrigerator until ready to mix into the horchata.
Pour the soaked almond mixture and all its contents into a large blender and add in the 3 cups of remaining water. Blend on high until completely smooth, about 2 to 5 minutes depending on the power of your blender. You may need to work in batches depending on the size of your blender.
Strain the blended mixture through a fine mesh strainer or nut milk bag to remove any solids. This may require straining 2 to 4 times to remove all the grittiness.
When completely smooth, pour it into a large pitcher and mix in the strawberry puree, milk, evaporated milk, granulated sugar, and vanilla extract. Stir until all the ingredients are well combined.
Serve over ice and top with ground cinnamon and chopped strawberries.
Notes
Make it silky smooth. I like to add the strawberry puree as is, but feel free to strain it into the pitcher using a fine mesh strainer.
Adjust the sweetness. You can adjust the sweetness of the horchata to your liking and use your favorite sweetener like honey, agave, brown sugar, or sweetened condensed milk. Just note the strawberry puree is also sweetened so it's best to taste as you go.
To make it dairy-free, use a dairy milk alternative like almond, soy, coconut, oat, or cashew milk.
To make it nut-free, you can simply omit the almonds. No need to replace them.
Ceylon cinnamon: Also referred to as "Mexican cinnamon." Ceylon cinnamon is light brown, fragile, and has a lot of layers that are easily broken, as opposed to Cassia cinnamon which is very hard and is not easily broken in half. Ceylon cinnamon can be easily found in Hispanic grocery stores or online. If you’re not using Mexican cinnamon, remove the cinnamon stick from the mixture before blending.
Separation of the water and the rice mixture is completely normal, especially if it's been sitting in the fridge for a day or two. Just mix it together with a large spoon and serve as you normally would.