One of my first brew sessions in my new apartment will be an imperial stout of which I plan on brewing a standard stout as partigyle.I plan on adding another kg of 2-row for the 2nd mash, but also want to make sure it keeps the black color, so was thinking about additionally capping it with some dark chocolate or roasted barley for the 2nd mash as well (same dark grains which are in the original grist). My question is, what would a good quantity be for capping a grist which for the 1st runnings had 0.6 kg of chocolate and 0.4 kg of roasted barley for a 5 gallon batch? Would 100 g of each do, or should I go higher/lower? I have no clue how much color will be left after the 1st runnings but I am assuming it will look more like a brown ale than a stout.
Black grains will be added at vorlauf for both of the runnings by the way, so in reality I am only mashing the original dark grains for little more than an hour.