In a shallow bowl or baking dish, whisk together the eggs, milk, sugar, vanilla, salt, and cinnamon until smooth.
Add the blueberries into the egg/milk mixture and use a fork to gently mash them in. Then let the mixture rest for 10 minutes to let the blueberry flavor infuse in.
Dip the bread, one slice at a time, into the mixture to soak it, turning a few times to make sure it is even.
Heat a large, nonstick skillet and melt ½ tbsp of butter per slice of bread. Depending on the size of your skillet, cook 1-2 slices at a time.
Once the butter is hot and sizzling, add 1-2 of the soaked challah slices and cook for 2 minutes on each side, or until golden brown. Repeat with the remaining slices.
Serve hot with more blueberries and maple syrup. Enjoy!