Step 1: Preheat your oven to 350°F (175°C). Lightly butter a 9x13 inch baking dish.
Step 2: Tear or cut your stale bread into 1-inch cubes. You should have about 6-8 cups. Spread the bread cubes evenly in the prepared baking dish.
Step 3: In a large bowl, mash the overripe bananas with a fork until mostly smooth, with a few small lumps remaining for texture.
Step 4: In another large bowl, whisk together the eggs, granulated sugar, brown sugar, milk, heavy cream, melted butter, vanilla extract, cinnamon, and nutmeg until well combined and smooth. Stir in the mashed bananas.
Step 5: Pour the banana custard mixture evenly over the bread cubes in the baking dish. Gently press down on the bread with a spatula to ensure all the cubes are submerged and have a chance to soak up the liquid.
Step 6: Let the bread pudding sit at room temperature for at least 15-20 minutes, or even up to 30 minutes, allowing the bread to fully absorb the custard. For deeper flavor and better absorption, you can cover it and refrigerate it for 1-2 hours, or even overnight.
Step 7: If using, sprinkle pecans or walnuts and/or chocolate chips over the top.
Step 8: Bake for 45-55 minutes, or until the top is golden brown and a knife inserted into the center comes out mostly clean. The center should still be slightly jiggly but not liquid.
Step 9: Remove from the oven and let it cool for 10-15 minutes before serving. This allows the pudding to set properly.