Of all my mother-in-law’s signature recipes for cakes, breads, cookies and pies, her Sour Cream Coffee Cake elicits the most nostalgia. So much so, the family handed it out on printed cards at her memorial service. Dorothy, or Dick as we all called her, passed away three years ago at the age of 91. She started out with the usual nickname, Dot, until her baby brother mangled it so adorably that the mutation stuck. I don’t know how much gender confusion it caused, but when she and my father-in-law Louis won a bridge tournament, the local newspaper reported their names as “Richard and Louise.” Dick first baked this sour cream coffee cake in the…