Preheat oven to 350°. Grease a 9x5-inch loaf pan (I used an 8 loaf pan).
In a large skillet, stir together banana, 1/2 cup brown sugar, 5 tablespoons butter, water, and 2 teaspoons brandy flavoring over medium-low heat. Cook until mixture begins to bubble.
Remove from heat; cool to about room temperature.
Once it is about at room temperature, place banana mixture in a large bowl.
Add buttermilk, remaining 1/2 cup brown sugar, eggs, and vanilla. Beat with a mixer at medium speed until well-combined.
In a medium bowl, whisk together flour, baking soda, salt, cinnamon, and allspice.
Add flour mixture to banana mixture, and stir just until blended.
Pour batter into prepared loaf pan coated (for the mini loaves, pour about 1/2 cup into each loaf).
Bake for 1 hour, or until a wooden pick inserted in center comes out clean (18-22 minutes for the mini loaves).
Remove from oven, and cool 10 minutes in pan on a wire rack.
Remove bread from pan, and place on wire rack to finish cooling.
(Optional) For the icing, whisk together powdered sugar, remaining 1 tablespoon melted butter, and remaining 1/2 teaspoon brandy flavor until well-blended.