Chocolate Marble Cake with Orange Icing

DIRECTIONS FOR CAKE:

1. Preheat oven to 350°F.
2. Line the base and the sides of a loaf pan with parchment paper. Spray the parchment paper that will touch with the batter.
3. Combine the flour and baking soda into a medium mixing bowl and set aside.
4. Combine the butter and sugar in a large mixing bowl. Beat together until pale and fluffy (about 3 minutes).
5. Add the eggs and vanilla, and beat until fully incorporated, about 2 to 3 minutes.
6. Add half of the flour mixture into the butter mixture. Mix to combine.
7. Add half the yogurt. Repeat with the remaining flour and yogurt, scraping the sides and bottom of the bowl to fully combine all the ingredients.
8. Separate a third of the batter into a clean bowl. Whisk cocoa powder and boiling water together.
9. Fold chocolate mixture into the separated batter until well combined.
10. Spoon dollops of batter into the prepared loaf pan. Alternate with spoonfuls of the chocolate batter and the plain batter, to form a checkerboard-like pattern.
11. Drag a knife through the batter in a swirling motion, to create a marble effect (do not over swirl; a few strokes will be enough).
12. Bake for 45 to 55 minutes, until the top springs back to the touch and a toothpick inserted into the center comes out clean.
13. Remove from the oven and allow the cake to cool for 10 to 15 minutes before turning it out onto a wire rack.

DIRECTIONS FOR ICING AND ASSEMBLY:

1. Prepare the icing while the cake is cooling. Whisk together half of the orange juice, zest, vanilla and powdered sugar.
2. Add teaspoons of additional juice gradually until you get a slightly thick but still runny consistency.
3. Pour icing over the slightly warm cake. Let it drip over the sides.
4. Slice the loaf into 8 equal slices. Store in an airtight container for up to a week.