Low gluten flour.
How to make butter cookies
Cut the butter into small pieces and let it soften to a paste at room temperature, push it with a spatula to feel no resistance.
Use a whisk to beat the butter, just lighten the color slightly, do not over beat
Pour in the salt and whisk a few times with a whisk.
Pour in the granulated sugar in two parts, add half and mix well with a whisk, then add the other half and mix well with a whisk, so that the granulated sugar is not visible, do not over whisk.
Add the egg yolks and mix well with a whisk.
Sift the low gluten flour and add it in batches, using a cutting motion so that the flour is absorbed by the butter, until all the flour is invisible
Prepare a piping nozzle and piping bag, pour the powder balls into the piping bag, line with parchment paper, and squeeze out the pattern on the tray
Preheat the oven to 120 degrees on the top and bottom, preheat for 15 minutes, place on a medium bake, 120 degrees on the top and 90 degrees on the bottom, bake for 30 minutes, then 150 degrees on the top, bake for 5 minutes to coat