In A Clash of Kings, Samwell Tarly says- "If I could fly, I'd be back at Castle Black eating a pork pie".
Before a modern cook attempted to recreate this recipe, they would have to decide whether to cook it based on a medieval or modern pork pie recipe. Medieval pork pies tend to be sweet with currants and ginger in them. Modern pork pies are far more dense, and are filled with more pork and fewer other ingredients. Given that Game of Thrones was written based on late-medieval history, it is probably more likely that Sam's pork pie was of the medieval type.