Cube bread into 1" pieces.
Mix all batter ingredients until well combined.
Gently toss bread in custard until fully coated.
Transfer bread to a greased 9" x 13" pan.
If you like, cover with foil and rest overnight (or continue for baking immediately!)
Mix up the streusel, first combining the dries then add in the butter.
Top bread mixture evenly with fruit (if using).
Sprinkle streusel evenly over the top.
Bake covered for 30 minutes, then uncovered for 15.
Allow to cool for a few minutes, then slice and enjoy with all the toppings!