PREHEAT oven to 350° F. Stir together crushed vanilla wafers and 6 tablespoons melted butter. Press onto bottom and sides of 9 ½- to 10-inch glass pie plate. Bake for 10 minutes.
MELT butterscotch morsels, 1 tablespoon butter and 6 tablespoons heavy cream in the top of a double boiler or glass bowl placed over simmering water, whisking until smooth. Set aside 3 tablespoons in a small cup and cover for later use. Spread the remaining ganache evenly over the pie crust then place in refrigerator.
PLACE bananas in medium baking dish. Drizzle with 2 tablespoons melted butter and sprinkle with 3 tablespoons brown sugar and cinnamon. Bake at 350° F, stirring occasionally, for 30 minutes or until bubbly and caramelized.
PLACE 1/2 cup milk in a medium mixing bowl and sprinkle with gelatin. Set aside to soften for 5 minutes. Bring remaining milk and evaporated milk to nearly a boil in a medium saucepan over medium heat, stirring often. Add 1/2 cup light brown sugar, cornstarch, and the egg yolks to the softened gelatin and whisk until blended. Gradually whisk about a 1/4 cup of the hot milk mixture into the gelatin mixture; repeat this process once or twice using about 3/4 cup of the hot milk mixture. Pour the warmed gelatin mixture into the saucepan with the hot milk and bring to a boil over medium-low heat, stirring constantly. Cook for a few minutes or until mixture is very thick and coats the back of a wooden spoon.
STRAIN cream mixture through a fine wire strainer into a large bowl; whisk in 2 tablespoons butter and vanilla extract. Stir in the roasted bananas. Cool at room temperature for about 30 minutes, then transfer to refrigerator for 1 hour to cool. Spread the filling over the ganache in the pie shell and refrigerate for at least 4 hours.
BEAT 1 1/2 cups heavy cream in a large bowl on high speed until foamy. Add the powdered sugar and 1/2 teaspoon vanilla extract and beat until soft to medium stiff peaks form. Spread over the pie. Transfer the reserved 3 tablespoons ganache into a small resealable bag. Seal bag, pushing out all the air, and press the ganache to one corner of the bag. Cut a very small hole in the corner and drizzle on the top of the pie. Keep pie refrigerated until ready to serve.