Beat butter and powdered sugar until fluffy.
This takes about three minutes.
Add vanilla extract and mix well.
The mixture should look creamy and light.
Combine flour, cocoa powder, and coffee powder.
Add salt to the mixture.
Whisk everything together thoroughly.
This removes any lumps completely.
Add dry ingredients to butter mixture slowly.
Mix until just combined together.
Fold in chopped walnuts gently.
Don't overmix the cookie dough.
Preheat your oven to 350°F.
Roll dough into one-inch balls.
Place them on baking sheets.
Bake for 12-15 minutes until set.
They shouldn't brown too much.
Let cookies cool for five minutes.
Roll warm cookies in powdered sugar.
Let them cool completely on racks.
Roll in sugar again for extra coating.