Combine 1 cup raw almonds and 3/4 cup short-grain white rice in a large bowl and cover with cool water by about two inches; soak for at least 4 hours or overnight.

Drain and rinse the soaked almonds and rice under cool running water for 30 seconds to remove sediment.

Transfer the drained almonds and rice to a high-powered blender; add 4 cups fresh filtered water.

Blend on high speed for 2 to 3 minutes, stopping to stir halfway, until mixture is completely smooth.

Strain the blended mixture through a fine-mesh strainer lined with cheesecloth into a pitcher or bowl; let drip for 5 to 10 minutes without pressing the solids.

Pour the strained liquid back into the blender and add 2 tablespoons maple syrup or agave nectar, 1 teaspoon vanilla extract, 1/4 teaspoon ground cinnamon, and a pinch of sea salt; blend on low for 30 seconds until combined.

Refrigerate the horchata in a pitcher for at least 2 hours until thoroughly chilled.

Stir or shake before serving; pour over ice and garnish with a pinch of ground cinnamon.