Soak the almonds and rice. Combine almonds and rice in a large bowl and cover with water. Leave at room temperature to soak at least 8 hours, or overnight.

Drain and rinse. Drain the almonds and rice through a fine mesh strainer and rinse.

Blend. Combine almonds, rice, sweetened condensed milk, and Matcha powder in a blender. Blend on high until the almonds and rice are very finely ground. If you don't have a high powered blender you may need to add 1/2 cup of water to get the blender going.

Add water. Add 2 cups of cold water and blend again. If you want the horchata completely smooth, strain out the rice and almonds through a fine mesh strainer. If you want it really smooth you can even line the strainer with a layer of cheesecloth. I prefer to leave them in because they add a nice thickness and viscosity.

Enjoy! Serve horchata over ice and enjoy. Any leftover horchata can be kept covered in the refrigerator up to a week.