Preheat your oven to 400 degrees and spray a 9x9" baking dish with cooking spray.
Tear 6 cups of bread into bite size pieces and place to the side.
In a large mixing bowl, whisk together 6 eggs, 1 cup whole milk, 1/2 cup heavy cream, 1 tbsp vanilla extract, 2 tsp cinnamon and 1 tsp lemon extract. Add bread and gently stir. Pour bread and mixture into baking dish.
Make the crumble topping by combing ½ cup of flour, brown sugar and sea salt in a medium bowl. Melt butter slightly and drizzle over the flour and sugar mixture while very gently and slowly stirring with a fork. Add in ¼ cup of flour at a time as needed to create a dry crumble but don't overmix! Stop as soon as you have crumbs that are more dry than wet.
Add the crumble to the top of the bread mixture.
Bake in the oven at 400 degrees for about 30-40 minutes or until the top is a nice golden brown and the custard has set.