Step 1

Preheat your oven to 325°F/167°C. Generously butter your loaf pan and line it with parchment paper.

Step 2

In a medium bowl, whisk together your flour, baking powder and salt. Set aside.

Step 3

In a stand mixer fitted with a paddle attachment, beat the butter for 1 minute on high speed. It should be smooth and creamy.

Step 4

Add your sugar and beat on high speed for 4 minutes. You want it to be very light and airy. Add your vanilla.

Step 5

Add your eggs one at a time, beating for 1 minute after each new addition and scraping down the bowl well before each addition.

Step 6

Add a third of your flour mixture and beat on your lowest speed. Add half of your sour cream, and again beat on low speed. Repeat the flour, sour cream and then the final addition of flour. Beat on low speed until combined after each new addition.

Step 7

In a small bowl, whisk your espresso powder with 1 tablespoon of boiling water. Take half of your batter into a medium bowl, and whisk it with the espresso and cocoa powder.

Step 8

Using an ice cream scooper, scoop out the vanilla batter into your loaf pan and alternate it with the chocolate batter, creating a checkerboard pattern. Repeat until you have used all the batter, I created two layers like this. Then use a butter knife or small offset spatula to create a few swirls. Do not over swirl it.

Step 9

Tap the loaf pan on your countertop a few times to get rid of any air bubbles.

Step 10

Bake for 1 hour and 10 minutes, a tester should come out clean. After 20 minutes, take out of the pan and let cool completely.

Step 11

In a small saucepan, bring your heavy cream to a simmer (not a boil!). Place your chopped chocolate in a medium bowl, and pour the heavy cream on top. Leave for 3 minutes. With a rubber spatula, swirl the two together until it is completely smooth. Sprinkle over your salt. Let it sit until it is a harder consistency, about 15 minutes. Spread on top of your loaf.