01 -  Preheat the oven to 375°F (190°C). Line a baking sheet with parchment paper. 
 02 -  In a bowl, whisk together the Greek yogurt, egg, honey or maple syrup, vanilla extract, and cinnamon until smooth. 
 03 -  Place the bread slices on the prepared baking sheet. Using the back of a spoon, gently press down the center of each slice to create a shallow well, leaving the edges intact. 
 04 -  Spoon the yogurt mixture evenly into the wells of each bread slice. 
 05 -  Top with fresh berries and, if desired, sprinkle with chocolate chips or drizzle with nut butter. 
 06 -  Bake for 12–15 minutes, or until the custard is set and the edges of the bread are golden. Let cool slightly before serving. Enjoy warm.