The Beginnings of Dinner

Our old (as in ex, not in age) neighbour from when we lived on the 15th floor is wifeless for a month.  Joe and his Ukrainian wife Veronika are expecting their first baby in August, and Veronika has flown home to visit with her family for the next few weeks.  Taking pity on his temporary bachelor state, we have invited him to come for a home-cooked meal tomorrow night, along with the new owners of our old apartment -- Joe's new neighbours.  I'm making "comfort food" -- a turkey shepherd's pie with buttermilk mashed potato topping.  This is the filling, which I'm making a day ahead so that all the flavours have a chance to mingle and meld.