Take butter, sugar, salt and baking powder in a big bowl.
Whisk it with a hand mixer or a regular whisk for about 3-4 mins or thill it becomes light in color.
Now add cashew powder and all purpose flour in 3 parts and fold it in.
After adding the last past of flour and cashew powder, use your had to make a dough ball. Dough should be soft but not sticky.
Dust the work surface with a little all purpose flour. Put the dough on it and roll it to make a cylinder roll.
Wrap the dough roll tightly in a cling wrap and refrigerate it for about 40 to 50 mins till the roll firms up a little.
Pre-heat the oven at 350 F / 180 C.
Take a baking tray and line it with parchment paper.
Get the dough roll out of fridge and take it out of cling wrap onto cutting board.
Cut cookies about ¼th inch thick and put it on the baking tray.
Press some broken cashews on the top of the cookies so that they stick in a bit and do not fall off after baking.
Do not take a lot of time to do this or the dough will start to soften.
Put the tray in the oven and bake for about 15 - 18 mins on a middle rack. till the cookies have a very light browning at the bottom. As the heating of all ovens vary, I would recommend to check the cookies at 12 mins and cook ahead depending upon requirement.
If you like soft cookies take the cookies out at 15 mins otherwise for crisper cookies bake till 18 mins.
Let them cool before storing them in a dry air tight container. They stay good for about 3 weeks.
Notes
Do not forget to refrigerate the dough roll before baking.
Chilling the cookie dough before baking solidifies the fats thus the cookie dough takes longer to melt and the cookies doesn't spread thin and rises well.
Sift the flour before using.
Don't cut the cookies to thin.
Do not roll the dough into a fat cylinder. Make it slender as the cookie will spread and expand while baking.
If after cutting the cookies and adding cashews on top you feel the dough has softened a lot then put it in refrigerator for another 10 mins before baking.