Grease a large 5-quart rectangular baking dish with butter or cooking spray.
Add the torn challah, fresh cherries, and chocolate chips to the baking dish. Toss gently to distribute.
In a large bowl, whisk together the Chocolate Silk Protein, eggs, and kosher salt until completely smooth.
Pour the custard evenly over the bread mixture, gently pressing the bread down so it absorbs the liquid.
Cover and refrigerate overnight, or let sit for at least 30 minutes.
Preheat the oven to 350°F.
Bake uncovered for 45–55 minutes, or until the casserole is puffed, golden brown, and set in the center.
Let rest for 10 minutes before serving.
Dust lightly with powdered sugar, if desired.