Preheat your oven to 325°F (163°C) and grease or line a loaf pan with parchment paper, leaving overhang for easy removal.

In a small bowl, mix the brown sugar, cinnamon, melted butter, salt and flour until you have a nice paste. Set to the side.

In a large bowl, add oil, granulated sugar and brown sugar. Mix until well combined. Add the eggs one at a time, mixing well after each, then stir in the vanilla extract. In a liquid measuring cup, add buttermilk and then stir in the sour cream. Mix gently until combined.

In a separate bowl, whisk together the flour, baking soda, baking powder, cinnamon, nutmeg, ginger and kosher salt. Add the dry ingredients to the wet mixture and gently fold just until combined. As you mix, slowly pour in the buttermilk mixture. Mix until just combined. Gently fold in the carrots.

Pour half of the batter into the prepared loaf pan. Then spoon half of the cinnamon sugar mixture all over the batter. Using a butter knife, gently swirl the cinnamon swirl mixture into the batter. Then repeat this step with the remaining batter and cinnamon sugar mixture.

Bake loaf for 50-60 minutes. It will be done when an inserted toothpick comes out mostly clean. Let the bread rest for at least 20 minutes- then remove from pan to cool for another 30 minutes.

To make the frosting, start by melting the butter in a saucepan over medium heat. Stir constantly as it foams, then watch for golden brown bits to form at the bottom and a nutty aroma to develop. Remove from heat immediately and pour the butter into a large heatproof bowl. Let that mixture cool for about 15 minutes.

Add the cream cheese to the cooled brown butter. Using a hand mixer, beat on medium speed. Gradually add the powdered sugar and mix in the vanilla bean paste. Whip until icing is smooth and homogenous. Once the bread is fully cooled, spread the frosting on top, slice, and enjoy.