Salvadoran Morro Seed Drink

Name: Salvadoran Morro Seed Drink
Cuisine: American, Latin American
Ingredients: 1 cup morro seeds (or a pre-made horchata morro mix if unavailable); 2 tablespoons white rice; 2 tablespoons sesame seeds; 2 tablespoons peanuts (unsalted, toasted); 1 tablespoon cocoa nibs or powdered cocoa (optional); 1 small cinnamon stick (or 1 teaspoon ground cinnamon); 1 teaspoon allspice or a few allspice berries; 4 cups water (divided); 1/2 cup sugar (adjust to taste); 1 teaspoon vanilla extract; Ice cubes for serving