Place rice in a heavy-bottomed dry skillet over a medium heat and toast, stirring constantly for 4-5 minutes or until the grains turn golden. Remove from heat and place in food processor bowl fitted with a steel blade.
Place almond slivers in the same pan; toast for 1 to 2 minutes, stirring frequently. Add sesame seeds and continue stirring until both are lightly toasted. Remove from heat and combine with the rice. Process together for 15 to 20 seconds or until a homogeneous meal is formed. Set aside to cool.
Cream butter and sugar with mixer until light and fluffy. Add eggs and vanilla, beating until combined. Gradually add flour, salt, baking soda and cinnamon to creamed mixture, mixing until well incorporated.
Fold cooled rice mixture into the batter. Using a one tablespoon scoop, drop cookie dough onto a parchment-lined baking sheet, leaving 2 inches between each. Bake for 12 to 14 minutes or just until edges begin to turn golden brown. Remove to a cooling rack; dust tops with powdered sugar. Store in a covered container.