Combine rice, almonds, cinnamon stick and water in a bowl; cover with plastic and let sit overnight (or a minimum of 4 hours). If you're pressed for time, heat the water and pour it over the rice, almonds and cinnamon, cool briefly and then proceed, however, it will not have a chance to develop as nice a flavour.
When ready to blend, remove cinnamon stick and pour into blender. Blend till smooth then pass through a cheesecloth* lined strainer. Press gently to extract all the liquid.
Rinse blender and return strained liquid to jug. Add ackee, sugar and vanilla. Blend till smooth, taste and add more sugar if desired.
Serve chilled over ice, dust with cinnamon powder if desired. (If using the whiskey, pour a shot over the ice into the glass before pouring the Ackeechata)
Enjoy!
Notes
*You may have to double up the cheesecloth so the holes are fine. Alternately, you can use a nut milk bag