Preheat your oven to 325°F (160°C).
Toast the sourdough bread until very crisp and dry, then pulse in a blender or crush into fine crumbs.
Press the sourdough crumbs into the bottom of a small, lightly greased ramekin to form a thin crust.
In a medium bowl, whisk together the Greek yogurt, whole egg, egg whites, vanilla extract, and half of the maple syrup until completely smooth.
Pour the yogurt mixture over the sourdough crust.
Bake for 25 to 30 minutes, or until the edges are firm but the center still has a slight jiggle.
While the cheesecake bakes, place the berries and the remaining maple syrup in a small saucepan over medium heat.
Simmer the berries for 5 to 8 minutes, mashing slightly, until the mixture becomes a jammy compote.
Remove the cheesecake from the oven and let it cool completely at room temperature, then refrigerate for at least one hour.
Top the chilled cheesecake with the warm or cold berry compote before serving.