In a large shallow frying pan over medium-high heat, melt the butter. Add bananas, then brown sugar, cinnamon and nutmeg. Stir. Add rum to skillet. Cook until bananas are caramelized and alcohol has cooked off, 4 minutes or so. Remove from heat.
Meanwhile, in a large saucepan over medium heat, bring milk to a simmer. In a large mixing bowl, whisk together sugar, egg yolks and cornstarch. Add a small amount of milk, whisking quickly to keep egg yolks from scrambling. Slowly add the remainder of the milk, whisking until combined. Return saucepan to medium-low heat, and pour pudding mixture back into pan. Cook pudding, stirring frequently, until thickened, 4-5 minutes or so. Stir in vanilla and butter. Pour into a clean bowl and fold in the bananas foster. Spoon into dish, and top with Nilla Wafers.
To make the meringue topping: Utilizing either a hand mixer or a stand mixer, beat egg whites, vanilla, and cream of tartar until soft peaks form. Add in sugar, a little bit at a time, until glossy peaks form. Spoon onto pudding, brûlée with torch. Top with cookies.