Preheat the oven to 350 degrees F.
Lightly grease a 9" x 13" pan or line with parchment paper.
(use cookie sheet for thinner brownies).
In a medium bowl mix cocoa powder, salt,
baking powder, espresso powder. (set aside).
In a saucepan set over low heat, melt the
butter, then add the sugar, stir to combine briefly just
till it's hot (about 110 degrees F to 120 degrees F) but not
bubbling. Don't worry if it separates, just stir to
recombine. Heating this mixture a second time will dissolve
more of the sugar, which will yield a shiny top crust on
Transfer the mixture to the dry
ingredients bowl. Stir, add vanilla, add the eggs, stirring
till smooth. Then add the flour and walnuts, again stirring
Spoon the batter into the prepared pan.
Bake for about 30 minutes, until a sharp knife poked into
the center reveals wet crumbs, but not raw batter. Remove
from oven and cool completely on a rack. Cut brownies to the
size you want, just remember to check your dosage per
brownie if you are using infused-butter.