Preheat your oven to 350°F (175°C).

In a large mixing bowl, whisk together 2 cups of all-purpose flour with 1 teaspoon of baking soda until well combined.

In another bowl, combine 1 stick of melted butter, 1/2 cup of white granulated sugar, 1/3 cup of sour cream, 2 large eggs, 3 medium-sized mashed bananas, and 1 teaspoon of vanilla extract. Whisk until smooth and creamy.

Gently pour the wet ingredients into the bowl containing the dry ingredients and stir just until combined.

Take a 9 x 5 inch loaf pan and spray it with cooking spray. Pour half of the batter into the prepared pan.

In a small bowl, mix together the optional swirl ingredients: 1/2 cup of brown sugar, 1 teaspoon of ground cinnamon, and 1/2 cup of chopped nuts if desired. Spread this mixture evenly on top of the batter in the loaf pan.

Carefully spread the remaining banana bread batter over the swirl layer.

Place your prepared loaf pan in the preheated oven and bake for 65-70 minutes. It's ready when a toothpick inserted comes out clean or with a few crumbs.

Once baked, let it cool in the pan for about 10 minutes before transferring to a wire rack. Whisk together 3/4 cup of powdered sugar, 3 tablespoons of milk, and 1/2 teaspoon of vanilla extract to create your drizzle. Pour it over the top.