Earls Beauty Inn 635 East Fort Avenue, Baltimore, MD 21230-4722(410) 752-3680. It is a beauty shop and ice cream parlor in Federal Hill. It is near where Jenna Bush lives. This is the place. I don't know their hours, but it is perfect.
I was going to recommend the old fashioned ice cream parlor on the first floor of the Smithsonian American History museum, but I couldn't locate it on the interwebs. Is my memory failing me, was I hallucinating, or did there used to be one there?