Currywurst Sauce

I first tried currywurst—German sausage doused in a curry-flavored ketchup and sprinkled generously with an almost sweet curry powder, often sliced and served with a hard round roll—at a little place called hallo berlin in my old neighborhood in manhattan. I’m not sure now if Hallo Berlin’s was smoked sausage or not, or how exactly it was served, but it was extraordinary, unlike anything I’d ever tasted. (Curry powder ... on sausage?) Many years later, my friend (and