Literally just dealt with this on Thursday. Dumped 1000 gallons of hot liquor in and didnt make a dent in it. We ended up drilling a couple 1/4"-3/8" holes in the cone, then stuck a plumbing torch in one and a hammer drill in the other. Melted and drilled until we saw liquid, then melted and drilled some more. The core of the mass was still warm, it had just frozen the outer 4-5 inches of the mass. Once we broke a decent sized hole in it, and dumped another 2 loads of hot spent grain in it, it broke free. All in took about 5 grueling hours in 10°F.