Grease a casserole dish (I used a 9" x 13") with butter.
Cube prepared bread into ~1” pieces and spread evenly in the bottom of the casserole dish.
In a mixing bowl, mix heavy whipping cream, eggs, vanilla extract, cinnamon, Swerve Confectioners, and salt until thoroughly combined.
Pour egg mixture evenly over the bread in the casserole dish and refrigerate for 3-4 hours (or overnight).
When ready to prepare the casserole, remove the casserole from the fridge and preheat the oven to 350 F. (If you're using a glass casserole dish, make sure the glass reaches room temperature before placing it in the oven.)
Place the casserole dish into the preheated oven and bake for 25-30 minutes.
While casserole is baking, make the topping by mixing the Topping Ingredients in a bowl until thoroughly combined.
Remove the casserole dish from the oven and sprinkle the topping evenly over the French toast mixture.
Return to the oven for an additional 15-25 minutes until the topping is browned and bubbly.
Serve plain or topped with dusted Swerve Confectioners, keto maple syrup, or keto whipped cream.
Notes
The nutrition facts for this recipe have been calculated using Brownberry Keto Bread.
So the egg mixture can fully soak into the bread, the bread must be dried out prior to making the casserole.
Slow dry: Lay the bread out on cooling racks (or baking sheets) and let it dry out for about four hours. Then, flip the bread over and leave it out for another four hours.
Fast dry: Lay the bread on baking sheets and bake for five minutes on each side at 275 F.