Combine rice, flour, tapioca flour, potato starch, and guar gum in a medium sized bowl.
Beat butter, shortening, and sugar on medium speed until light and fluffy. Scrape the bowl. Add pandan paste and beat until combined. Beat in as much of the flour as you can with the mixer. Stir in remaining flour. Knead slightly to form a ball.
Press dough into pan cavities, filling two thirds full.
Bake in 350°F (180°C) oven for 7 to 8 minutes. Cool in pan for 10 minutes. Remove and allow cookies to cool completely on a wire rack. Decorate as desired.