Prepare filling: whisk sugar, flour, cornstarch and salt in heavy saucepan until no lumps remain. Gradually whisk in milk. Add yolks and whisk to blend. Scrape in seeds from vanilla bean; add bean.
Whisk over medium-high heat until cream thickens and boils 1 minute. Remove from heat and whisk in butter and rum. Remove vanilla bean. Transfer mixture to bowl and press plastic wrap onto the surface. Chill until firm for at least 4 hours.
For crust: combine wheat pastry flour, chocolate chips, bread flour, cocoa powder, sugar, baking powder and salt into processor. Blend until finely ground. Transfer to large bowl. Using fork, cut in butter until mixture resembles coarse crumbs. Mix orange juice, 1 tablespoon ice water, and vanilla in small bowl. Sprinkle over chocolate mixture, tossing until dough comes together in clumps and adding more water if dry. Using floured hands, gather dough into ball. Flatten into disk and wrap; chill for at least 2 hours.
Preheat oven to 375F degrees. Spray 9-inch glass pie dish with nonstick spray. Roll out dough between 2 sheets of parchment paper to 12-inch round. Peel off top parchment. Using bottom parchment as aid, turn dough over into prepared dish. Peel off parchment. Fold overhang under and crimp crust edges decoratively. Pierce crust all over with fork; freeze for 10 minutes.
Line crust with foil and fill with dried beans. Bake crust 20 minutes. Remove foil with beans. Contine to bake crust until dry and firm to touch (10 minutes longer). Cool crust completely on rack.
Spread 1 cup pastry cream over bottom of crust. Slice enough bananas into 1/4-inch thick rounds to cover cream in overlapping circles. Cover bananas with remaining pastry cream. Cover and chill for 3 hours.
Slice 3 more bananas on slight diagonal into 1/4 inch thick ovals. Arrange in overlapping circles on top of pie. Sprinkle with sugar.
Carmelize, if desired, using handheld torch. Alternatively cover bananas with whipped cream, sprinkle with chocolate sprinkles, and garnish with additional banana slices.