Pre-heat your oven to 375 degrees.
Line a rimmed baking sheet with aluminum foil and place a wire rack on top. Spray the rack with cooking spray and arrange the bacon in an even layer. Transfer the bacon to the oven and bake for 30 minutes until golden brown and crispy. Carefully remove bacon from the oven and transfer the strips to a paper towel lined plate to drain. When cool, crumble into small pieces and briefly set aside.
Slice the challah into 8 pieces about ¾-inches thick.
Now it’s time to “stuff” your French toast, which essentially means making Nutella and bacon sandwiches. For each sandwich: Spread one side of two pieces of bread with a heaping teaspoon of Nutella. Sprinkle 2 pieces of crumbled bacon on one of the slices of bread. Sandwich the two pieces of bread together, making sure that they are well sealed.
In a shallow baking dish, whisk together the eggs, half and half, whole milk, brown sugar, cinnamon, and salt. Set it on the counter next to the stove. Place a large pan over medium-low heat.
Add two of the Bacon-Nutella sandwiches to the custard mixture and let soak for 1 minute. Use a spatula to flip the sandwiches over and soak for 1 more minute on the other side.
While the bread is soaking, add 1 tablespoon of butter to the pan. When it’s melted and foaming slightly, remove each sandwich from the custard, holding it over the baking dish for a few seconds to let any excess custard drip off. Place the sandwiches gently in the pan and cook for 3-4 minutes on each side until golden brown. (Keep a close eye on your French toast while it cooks, friends! Burning it is a bummer.)
When the first batch of stuffed French toast is almost finished cooking, place the remaining two sandwiches in the custard to soak. Repeat the cooking process with the second batch.
Serve your Bacon and Nutella Stuffed French Toast warm. Top with powdered sugar or drizzle with maple syrup and brace yourself…