Preheat your oven to 325°F.
Pulse the sourdough bread in a food processor until it forms fine crumbs.
Toast the bread crumbs in a small skillet with the butter over medium heat until they are golden and crisp.
Press the toasted crumbs firmly into the bottom of a 4-inch springform pan or a small oven-safe ramekin.
In a blender, combine the Greek yogurt, cottage cheese, egg white, monk fruit sweetener, and vanilla extract.
Blend on high until the mixture is completely silky and no cottage cheese curds remain.
Pour the cheesecake batter over the sourdough crust.
Bake for 35 to 40 minutes until the edges are set but the center still has a slight jiggle.
While the cheesecake bakes, place the berries in a small saucepan over medium-low heat.
Simmer the berries for 10 minutes, stirring occasionally, until they break down into a thick, bubbling compote.
Remove the cheesecake from the oven and let it cool to room temperature, then refrigerate for at least 2 hours.
Top the chilled cheesecake with the berry compote before serving.