I wish I had a more straightforward answer, but honestly, the names are often used interchangeably and it can be pretty confusing. Boston cream donuts are always topped with chocolate and filled with pastry cream, just like a Boston cream pie or my Boston cream cupcakes. Most of the time, Bavarian cream donuts have the same custard filling (sometimes its lightened up with whipped cream or sometimes its thicker), but instead of being topped with chocolate, they are dusted with powdered sugar or coated in granulated sugar. I have seen Bavarian cream donuts out there that have a chocolate topping too, and that's where things get confusing. Regardless of what you call them, they're an indulgent, cream-filled treat that practically begs to be bitten into!