Prepare the Banana Bread: Preheat oven to 350°F. Beat 1 cup softened butter with a heavy-duty electric stand mixer at medium speed until creamy. Add 2 cups brown sugar, and beat until light and fluffy. Add 3 eggs, 1 at a time, beating just until blended after each addition. Add sour cream and vanilla, and beat just until blended.
Stir together flour, baking powder, baking soda, 1 teaspoon cinnamon, and 3/4 teaspoon table salt. Gradually add flour mixture to butter mixture, beating at low speed just until blended. Stir in mashed bananas and toasted chopped pecans just until blended.
Grease 2 (8- x 4-inch) loaf pans with vegetable shortening, and dust with flour. Divide batter evenly between 2 prepared pans. Bake in preheated oven until a wooden pick inserted in center comes out clean, 50 minutes to 1 hour. Cool in pans 10 minutes. Remove from pans, and cool completely on wire racks, about 1 hour.
Preheat oven to 350°F. Slice 1 loaf into 11 (1/2- to 3/4-inch) slices. Wrap other loaf in plastic wrap; reserve for another use. Place 11 slices on a baking sheet; brush each with melted butter. Bake in preheated oven until browned, 20 to 25 minutes. Set aside.
Prepare the Custard: Whisk together 4 eggs, 1/4 cup brown sugar, 1/4 teaspoon table salt, and 1/4 teaspoon cinnamon in a large bowl until blended. Whisk in milk and cream until well blended.
Prepare the Casserole: Lightly grease an 11- x 7-inch baking dish with cooking spray. Cut 4 toasted banana bread slices in half. Place remaining 7 toasted banana bread slices, slightly overlapping, in prepared dish. Place half slices, overlapping slightly, alongside whole slices, filling dish completely.
Slowly pour custard mixture evenly over bread slices. (The baking dish will be very full.) Cover and let stand at least 1 hour or overnight to allow bread slices to absorb the custard.
Preheat oven to 350°F. Uncover casserole. Bake in preheated oven until set and lightly browned, 55 to 60 minutes.
Pour half of the Honey-Banana Topping evenly over the casserole; serve with remaining topping.