Note: You can substitute an equal amount of shredded Swiss, Gouda, or pepper jack cheese for the cheddar.
Adjust oven rack to upper-middle position and heat oven to 475 degrees. Cook bacon in 8-inch nonstick, ovensafe skillet over medium heat until crispy, 5 to 7 minutes. Using slotted spoon, transfer bacon to paper towel-lined plate. Pour off all but 1 tablespoon fat from pan.
Add half of bread to skillet and cook over medium heat, stirring frequently, until golden brown, 3 to 5 minutes. Transfer to medium bowl and toss with untoasted bread.
Whisk cream, eggs, salt, and pepper in second medium bowl until smooth. Stir in scallions, cheddar, and bacon. Add egg mixture to now-empty skillet and cook over medium heat, using spatula to scrape bottom of pan, until eggs are just beginning to set, about 1 minute. Fold in bread and lightly pat mixture into even thickness. Bake until puffed and golden brown, 7 to 9 minutes. Serve.