In a large saucepan over medium heat, melt the butter.
Add the brown sugar, cream, and dark rum, cooking just until the brown sugar is mostly dissolved.
Fold in the banana slices.
Pour into a lightly greased 9x13 glass baking dish, and spread the banana slices around evenly.
Scatter the croissant pieces evenly over top of the banana mixture.
In a medium bowl, combine milk, eggs, coconut, and dark rum.
Pour mixture evenly over the croissant pieces.
Cover with foil and bake at 350 degrees for 30 minutes.
Remove foil, sprinkle with pecans (optional), and return to oven for 5-7 minutes or until a toothpick inserted near center comes out clean.
Remove to a wire rack.
Allow to cool for at least 20 minutes before inverting the casserole onto a serving dish.
Serve warm and DEVOUR!