First off, I believe that the delineation between shepherd and cottage and farmer is in great part a regional issue. In my neck of the woods, if you go into a restaurant and order Shepherd's Pie from the menu, you will almost always be served a beef-based pie. If you invite us to dinner and tell us that you will be serving Shepherd's Pie, we will not be expecting lamb.  More to the point though, I have been making this casserole and calling it Shepherd's Pie for two decades, so I'm sticking with it. Bottom line: this the best in cozy comfort food, no matter what you call it!  Hope that clears everything up for everyone.