Sift the rice flour, cornstarch and icing sugar into a mixing bowl.
Cut the butter into small cubes and add it to the dry ingredients. With your hands or a mixer, combine until you get a texture that resembles sand. The smaller the butter pieces, the better.
Add the egg to the mixture and mix it until the dough starts to come together.
Transfer the dough onto your work bench and gently knead it until it forms a smooth and homogenous ball.
Flatten the dough into a disc, warp it in plastic wrap and place it in your refrigerator for at least 30 minutes.
Once your dough is chilled, place it onto your slightly floured work bench and roll it. Place it in a 16cm tart form. Put it back into the refrigerator or freezer for another 30 minutes. The dough should be as cold before baking.