To make the sauce, start by placing butter in a microwave-safe bowl; microwave, covered, until melted, about 30-45 seconds.
Firmly pack 1 1/3 cups of light brown sugar and add into butter with coconut cream, allspice, cinnamon, and pecans (optional). Add sliced bananas, stirring gently to coat.
Transfer sauce and bananas to a greased 13×9″ baking dish (we used butter to coat the pan, you could use Pam too). Arrange bread over top, laying each piece on top of each other almost like stacked playing cards, trimming to fit as necessary.
Create the egg/custard mixture for the top of the French toast by whisking together the second set of ingredients above, just until blended or combined. Pour over the bread.
Refrigerate, covered, 8 hours or overnight.
In the morning, preheat oven to 375°F.
Remove the french toast from refrigerator while oven heats. Bake, uncovered, until a knife inserted in the center comes out clean and hot, about 35-40 minutes.
Let stand 5-10 minutes before gently (but quickly) flipping over onto a tray larger than the pan you baked it in.
