They say the secret to a good beer is in matching the style of the brew to the minerals of the water, and the good news for fans of the Black Stuff is that our natural Sauble groundwater is really quite similar to the municipal water in Dublin. This recipe was posted to the Internet newsgroups, and while I haven't tried it (yet) it's next on my list -- mostly I just wanted to test the recipe form, and, well, someone already mentioned the black stuff

Single infusion mash at 150F for 60 minutes, and of course, hold out 1/2 gallon of first runnings, add too it a few grains of raw malt, and at kegging or bottling time boil it and add it into the main batch. And don't be afraid of the horrible smell. Use irish moss if you like, and lots of chalk if your water is low. It won't readily dissolve, so you can stir a couple of teaspoons right into the mash.

To avoid the inevitable thread on water treatment, mash pH, solubility of CaCO3, and the like, DON'T FORGET, the alkalinity of all of this chalk is only going to buffer the acidity from, the large amount of roast. DON'T go and acidify your strike water to dissolve it, or you defeat the purpose.