Preheat the oven to 200 ° F.
Place the slices of bread on a baking sheet lined with parchment paper and bake for 15 to 20 minutes, turning the slices halfway through cooking, until completely dry. Remove from the oven, let cool and cut the slices of bread into cubes.
In a bowl, whisk the eggs with the milk, maple syrup, vanilla and cinnamon. Add the bread cubes and toss to coat them well with the egg blend. Add the berries and toss gently. Sprinkle small pieces of cookie dough (equivalent to 5 tsp)
Butter a 20-cm (8”) baking dish, then pour the mixture into it. Cover and let rest in the fridge for 8 to 12 hours, or overnight.
When ready to bake, preheat the oven to 350 ° F.
Bake the French toast casserole in the oven for 35 to 40 minutes.
Set the oven to “broil” and continue cooking, 2 to 3 minutes, until the top of the casserole is golden brown.