Rinse the rice under cool running water until the water runs mostly clear.

Add the rinsed rice to a large jar or bowl.

Add the cinnamon stick and 3 cups of water.

Stir, cover, and let the rice soak at room temperature for at least 4 hours, or ideally overnight for 8–12 hours.

Remove the cinnamon stick and reserve it.

Transfer the soaked rice and soaking water to a high-speed blender.

Add the remaining 1 cup of water, vanilla extract, maple syrup or sweetener, and fine sea salt.

Blend on high speed for 1–2 minutes, until the mixture looks milky and the rice is broken down very finely.

Taste and adjust sweetness if needed. The horchata base should taste slightly sweeter than the final drink because ice will dilute it.

Place a fine-mesh strainer lined with cheesecloth or a nut milk bag over a large bowl or pitcher.

Pour the blended rice mixture through the strainer in batches.

Press or squeeze well to extract as much liquid as possible.

Discard the rice pulp or save it for another use.

Place the cinnamon stick back into the strained horchata base for extra flavor while it chills.

Cover and refrigerate the horchata base for at least 1 hour, or until well chilled.

When ready to serve, sift the matcha powder into a small bowl or measuring cup to remove clumps.

Add the hot water. The water should be hot but not boiling, around 175°F.

Whisk briskly with a bamboo whisk, milk frother, or small whisk until the matcha is smooth, dissolved, and slightly frothy.

Fill serving glasses with ice.

Add a splash of oat milk, almond milk, coconut milk, or dairy milk if you want an extra-creamy latte.

Pour the chilled horchata over the ice, filling each glass about two-thirds full.

Slowly pour the whisked matcha over the top for a layered look, or stir it in for an even green color.

Garnish with a light dusting of matcha powder or ground cinnamon if desired.

Serve immediately with a straw or spoon for stirring.