1. Leave bread slices out, at room temperature at least 3 hours, or until slightly stale.
2. Generously coat a 9-inch baking dish with cooking spray. Arrange bread, slightly overlapping.
3. In large bowl, whisk eggs, heavy cream, milk, Gruyère, 1/3 cup maple syrup, cinnamon. Add chopped bacon, saving 2 tablespoons for later. Pour all over bread in baking dish. With hands, press down on bread to submerge.
4. Cover baking dish with plastic wrap. Refrigerate at least 5 hours or overnight.
5. Preheat oven to 375°F. Remove plastic. Sprinkle remaining bacon and Swiss cheese all over top of bread mixture.
6. Bake 45 to 50 minutes or until golden brown and set.
7. Top with blackberries and dust with powdered sugar before serving.