Preheat oven to 350 degrees and spray a 9 x 13 inch casserole dish with non-stick spray. Spread the cubed bread into the prepared dish and set aside.: As the oven warms to 350 degrees , you will notice the kitchen begin to warm and a dry, toasty scent that signals readiness. Spraying the dish prevents sticking and helps the edges crisp evenly. I like to place the rack in the center so heat circulates around the casserole, promoting uniform browning. A common mistake is skipping the spray and then struggling to serve portions cleanly, so take the extra minute to prepare the pan.
In a mixing bowl, combine all remaining ingredients, except blueberries, and whisk well. Pour the mixture over the bread cubes until all parts of the bread are moist. Sprinkle the blueberries on top and gently toss with the bread.: When you arrange the cubed bread , you should hear gentle rustling as the pieces nest together. Spreading the cubes in a single layer ensures the custard can reach every nook. I press pieces lightly so there are small pockets for the custard to soak in. Avoid packing the bread too tightly, because that can prevent even soaking; leaving a bit of air space helps the custard penetrate uniformly.
Bake for 30 to 40 minutes or until there is no liquid between the bread cubes and the casserole is lightly browned. Serve and enjoy!: As you whisk egg whites , coconut milk , pure maple syrup , vanilla extract , almond extract , and ground cinnamon , watch the mixture become glossy and slightly thickened. The aroma of maple and spices will lift as you whisk, giving a good preview of the baked result. Whisking well ensures the sweetener dissolves and the extracts distribute evenly, which prevents pockets of intense flavor. One pitfall is under-whisking, which can lead to inconsistent custard texture.
Pour the mixture over the bread cubes until all parts of the bread are moist: When you pour, listen for the soft splat as the liquid hits the bread. Let it sit for a few minutes so the custard is drawn into the cubes; you may gently press a few pieces to encourage absorption. You want the bread to be uniformly moist but not soggy on the surface. A helpful cue is to press the center gently with a spoon and observe that the custard has disappeared into the bread. Over-soaking can lead to a pudding like interior that will not hold shape, so aim for thorough but controlled absorption.
Sprinkle the blueberries on top and gently toss with the bread: As you scatter the blueberries , their color will create attractive contrast against the pale custard. Gently folding them in avoids bursting too many berries and turning the custard purple. If using frozen berries, sprinkle them straight from the freezer to minimize bleeding. A frequent error is stirring vigorously, which releases too much berry juice and can alter the custard color and consistency.
Bake for 30 to 40 minutes or until there is no liquid between the bread cubes and the casserole is lightly browned: During baking you will notice the aroma evolve, becoming richer and more caramel like as the top browns. Look for bubbling edges and a golden surface; inserting a knife into the center should come out mostly clean with just a touch of moistness. The interior will be set but still tender. If the top browns too quickly before the center sets, tent with foil to prevent overbrowning. Underbaking leaves a runny middle, while overbaking will dry the casserole, so aim for that sweet spot of set yet moist.
Serve and enjoy!: Once out of the oven the top will give a satisfying low crackle as it cools slightly. Allowing a few minutes to rest helps the custard settle and makes serving neater. The flavors will continue to meld during this short rest, and the temperature will be perfect for immediate enjoyment. A common misstep is serving piping hot right away which can cause portions to fall apart; a brief rest prevents that.
