Preparation
Lightly butter an 8-inch square Pyrex baking dish or mold that fits the bananas comfortably.
In a large bowl, combine the bananas with the sugar, lemon juice, rum, vanilla, and nutmeg, toss to coat well, and transfer to the prepared baking dish.
(You can prepare the recipe ahead up to this point, and refrigerate).
Preheat the oven to 350 F.
In a small saucepan over low heat, melt the butter, then remove from the heat and stir in the crumbled cookies and walnuts.
Sprinkle the crumbs over the bananas and bake until golden brown, 20 to 25 minutes.
If you add the peanut brittle, sprinkle it over the dish during the last 5 minutes of baking.
Serve hot.