Lightly grease a 9x13 inch-baking dish with nonstick cooking spray or butter.
In a large bowl, whisk together eggs, milk, cream, sugar, vanilla, cinnamon and salt.
Halve croissants horizontally (like a sandwich) and spread them with a thin layer of Nutella. Arrange them snugly in the pan.
Pour over half of the egg mixture.
Add the remaining croissant sandwiches over the top and pour remaining egg mixture over the croissants. Cover and place in the fridge for 30 minutes or overnight. Making this the night before is perfect.
When ready to bake, remove baking dish from the refrigerator and let stand for at least 15 minutes to get the chill off.
Preheat oven to 375°F (175°C).
Top croissants with thinly sliced butter and dust with cinnamon and sugar.
Transfer to the oven and bake for 35-45 minutes or until croissants are golden. If the tops of the croissants begin to brown too quickly, tent the top of the pan with foil.
Serve croissant french toasts warm with powdered sugar, and fresh sliced strawberries.
