Lightly roast the slivered almonds on the stove top, in a large skillet over low to medium heat, stirring often, just until they turn a golden hue. Let the almonds cool down.
Place the almonds and the rest of the ingredients in the blender and process until smooth.
Pass through a fine mesh strainer or cheese cloth, squeezing to get as much liquid as possible.
Pour into a pitcher with some ice. Add ground cinnamon if desired. Serve cold. Keep refrigerated. Stir before serving, as the heavier ingredients will sink to the bottom.
