Two wort batches from same grain bill?

[gbevs]

I'm looking to get two full 5 gallons worts from one grain bill/ mash. Looking for tips. My plan is to make an imperial stout (based off of Yeti recipe) with 17 lbs of 'base malt' (2 row pale). I planned on doing a regular mash and sparge with just the base malt and steep my specialty grains as I would with a partial mash technique. Then I'd like to get more use out of my 17lbs of base malt and do another mash/sparge to make a kinder/gentler beer. I was actually hoping to base it loosely on Bell's Two Hearted Ale but realize it will probably be a bit 'lighter', however I have some DME on hand and also wondered about adding crystal malt or other. More importantly, HOW to handl this second mash/sparge? I was told simply to the same amount of water as my first mash but at around 170 degrees (closer to sparge temp) than at 153 degrees and then do the same with a second amount of 'sparge' at 180 degrees? Or, should I just add as much water at around 170 as it takes to collect my second wort and just let it ride? Anyone done anythig like this? Got any pointers?

 

[Limited Visibility]

Its called a parti-gyle

check this out

 

[MacBruver]

Parti-gyle - Home Brewing Wiki

Search around a bit for parti gyle... lots of info.

(edit) ha! beat to the punch

 

[Limited Visibility]

I win 567890

Cant give any valuable info for ya though other than search around on here or elsewhere. My tun is way to small to try these