This vegan babka replaces the eggs that are traditional to brioche dough with mashed banana and butter with coconut oil. The dough proofs overnight, which may seem like it draws the process out, but I actually find it to be easier, especially if you plan to serve it in the morning. Chocolate babka makes a special addition to a brunch spread and a totally legitimate afternoon snack. Using good chocolate is well worth it in this application. Recipe inspired by Kim Boyce's chocolate babka.