Dice the butter into 3 cm cubes, put into a heatproof bowl and microwave slightly at 600W. (Just until the butter starts to melt around the edges - be careful not to melt it too much!)
Mix butter with a whisk until creamy. Add sugar in 2 batches, mixing well each time. When the batter becomes light-colored and fluffy, add the egg and mix well.
Sift the cake flour into the bowl and, using a rubber spatula, mix lightly with a cutting motion. It will be dry and hard to mix at first, but gradually the dough will come together.
When the dough comes together, flatten and wrap in plastic wrap. Let it rest in the refrigerator for about 1 hour. You can also bake the cookies right away without letting the dough rest; they will be moist and delicious.
Take the dough out and put it on a surface dusted with flour. Roll the dough into a cylinder 4 5cm in diameter. Wrap in plastic wrap and let it rest in the refrigerator for 1 more hour. You can also store the dough in the freezer.
Preheat the oven to 340F/170C. Cut the dough into slices about 8 mm thick and place on a baking sheet lined with parchment paper. Bake for about 15-20 minutes at 340F/170C.
In Step 5, you can also roll the dough out with a rolling pin and cut it out with a cookie cutter.
Story Behind this Recipe
This recipe uses a ratio that's easy to remember: Flour: Butter: Sugar: Egg = 3 : 2 : 1 : 1. My mom and I often make these cookies together. My mom even spent two days baking these cookies to use as wedding favors for my wedding. Relatives, friends, and co-workers have given these cookies rave reviews, so I'm really proud of this recipe.
If you let the dough rest in Step (4), the cookies will be crispy. If you bake them without letting the dough rest, they'll be soft and moist. Make them whichever way you like! I like them golden brown, so I bake them a bit longer. My mom always says she wants to use the butter for cooking other things too, so we use salted butter . Of course you can use unsalted butter - just add a pinch of salt!