So I went out Tuesday and bought a frozen haggis. 1.5 kg. I had a heck of a time tracking it down, and walked for about an hour before I found the meat shop. Anyway, my question is this: I'm going to cook it by following P1M's Haggis Ferintosh recipe, which calls for a pre-boiled haggis. How long do I boil the thing for? It's thawing on the counter now, so it won't go in the water frozen (at least not entirely - the thing was like a stone).

Help?