The brownies already taste very dark without it, similar to 72 % dark chocolate, because you'll
add equal amounts of flour and cocoa powder to the batter.
In the interest of simplicity, I'll suggest you maintain this starter the way I suggest starters be maintained throughout this site (feed them no less than twice a day while the starter is at room temperature,
feed equal amounts of flour and water by weight, and each feeding should be enough to double the size of the starter.)
Or do you sub the starch with
an equal amount of flour?
(vegan) butter in a pan, add
an equal amount of flour.
of sourdough starter added to the water from the recipe and
an equal amount of the flour from the recipe.
Instead I made a thick paste from
the equal amount of flour and sugar, and a bit of water.
You can leave out the pecans, but use and
equal amount of flour.
or just
the equal amount of flour for the bread or the streusel?