Adapted from recipe on Adventures in Homebrewing site: https://blog.homebrewing.org/russian-imperial-stout-recipe-extract/
Batch size is 7L at 1.100 but there is 180g each of roasted barley and chocolate malt cold steeped for 48 hours in 5x their weight of water. This results in 1.5L of black stuff which is added at the end of the boil and doesn't add any gravity. This means that the rest of the recipe is for the equivalent of 5.5L at 1.127 (i.e. 127*5.5/7=100) so we're aiming for a boil size of 10L at 1.070, which will have a long boil and get down to 5.5L before adding the black stuff to bring back to 7L.
simpson drc, mash at 158f