Whole milk and sweetened condensed milk make this booze-infused Mexican horchata insanely rich and creamy.
In a medium-sized bowl, combine rice and warm water and set aside for 30-60 minutes. Drain the rice through a sieve, retaining the water. Transfer rice to a food processor or blender with 1/2 cup of the retained water. Add the cinnamon, and blend on high for 2 minutes, or until a smooth paste forms. Transfer the paste to bowl with the retained water and whisk well. Let the mixture stand for 2-4 hours, whisking occasionally.
Strain the rice milk through a fine sieve into a jug or bowl. Add the milk, sweetened condensed milk and vanilla and blend well. Pour horchata into glasses filled with ice, leaving space at the top for rum. Mix in 2 ounces spiced rum per glass. Sprinkle with fresh nutmeg, if desired.