Thanks to Jaime-Leigh Gorham for sharing her simple and delicious recipe!
Cream:
114 gm unsalted butter
140 gm sugar
When butter and sugar are creamy, blend in:
1 egg
1 t vanilla
Set aside.
Sift together:
260 gm all-purpose flour (中力粉 churikiko in Japanese)
½ t baking powder
½ t salt
Add sifted ingredients to the butter/sugar mixture. Don't overmix. Wrap in plastic and chill for at least 30 minutes.
If you want to save some dough for another day, wrap it in plastic and put it in a ziplock freezer bag in the freezer.
Preheat oven to 180ºC (350ºF).
While the oven is heating, put a little flour on a clean surface and a little on a rolling pin. Roll the dough to 5-7mm thickness. Use cookie-cutters to cut.
Place cookies on a parchment-covered tray and bake for 10-15 minutes, depending on the size of the cookies. The cookies should be only lightly brown. Cool on a cooling rack.
When cookies are completely cooled they can be iced.
Icing
Mix together:
250 gm powdered sugar
1 egg white
1 t lemon juice
If you are going to make a small batch of cookies, you won't need so much icing. Instead, place a pile of powdered sugar in a small bowl, add part of an egg white and a squeeze of lemon. Mix. Add more sugar as needed to make the right consistency for icing.
Divide the icing and mix in a tiny bit of a different color food coloring to each bit. Put icing in the corner of a small plastic bag. Push the icing towards the corner. Cut the tip of the corner. Do this with each of the colors. You now have icing "pens" with which to decorate your cookies.
Wait until the icing on the cookies is completely dry before serving or storing.