Rinse 1 cup long-grain white rice under cold water until rinse runs clear to remove excess starch. Transfer rinsed rice to a medium heatproof bowl. Pour 1 cup hot (not boiling) water over the rice to cover and let it sit 30 minutes to soften. The water will cool; this extracts flavor.

Blend

After soaking, add the rice and soaking water to a blender along with 1 cup whole milk, 1 tsp ground cinnamon, 1/2 cup granulated sugar, 1 tsp vanilla extract, and 1/8 tsp fine sea salt. Blend on high for 1 to 2 minutes until mixture is very smooth and rice is broken down.

Strain

Place a fine-mesh sieve lined with a double layer of cheesecloth (or a nut milk bag) over a large bowl or pitcher. Pour the blended mixture through the cloth, letting the liquid drain naturally. Press gently with a spatula to extract as much liquid as possible but avoid forcing gritty solids through. Discard solids leftover in the cloth or use sparingly in baking.

Taste and adjust

Taste the strained concentrate. If you prefer it sweeter, dissolve up to 1-2 tablespoons additional sugar into the warm concentrate. If more cinnamon is desired, stir in an extra 1/4 tsp ground cinnamon. Let concentrate cool to room temperature (about 15–20 minutes).

To Finish (makes ~32 fl oz)

Combine and chill: Pour the horchata concentrate into a 32 fl oz (1 quart) pitcher. Add 3 cups cold water and stir until fully combined. Taste and adjust dilution — add up to 1/2 cup more water if you prefer a lighter flavor, or a splash more milk for creaminess. Refrigerate for at least 1 hour to fully chill and allow flavors to marry.

Serve: Fill glasses with ice if desired. Stir the chilled horchata again and pour into glasses. Sprinkle a light dusting (about 1/8 tsp total) of ground cinnamon over each glass or the pitcher for garnish.

Storage: Store leftover horchata in a sealed container in the refrigerator for up to 3 days. Shake or stir before serving because separation may occur.