Yes, the Malzmühle! Best place to go to eat. It's a little bit further away than the other places, IIRC. I remember it as being one of the few that had wheat in it. It wasn't my favorite Kölsch, but it did have the best meal.
OK, Gordon's tip for Köln. Get off the train at the Hauptbahnhof, go straight to Früh, pausing momentarily to look at the Dom. Do your style calibration there, then when hungry head towards the Malzmühle for dinner, stopping at whatever places you hit on the way. Have the schweinhaxe, but you might want to consider sharing it. It's a football of meat with a huge knife stuck in the side of it. Crispy, crackling skin over luscious pork. Eat the whole thing and you'll be done for the night. Split it, and you'll be able to keep drinking.