- PREHEAT oven to 350F and spray a 9 × 5-in. loaf pan with oil.
- WHISK flour, sugar, baking powder, baking soda and salt in a large bowl. Whisk eggs, buttermilk, butter, hot water and vanilla in a medium bowl. Stir into flour mixture until just combined. Reserve 1 cup of the batter.
- MELT chocolate chips and 2 tbsp hot water. Stir into reserved 1 cup batter until no streaks remain. Pour half of the plain batter into prepared pan. Top with chocolate mixture, then cover with remaining plain batter. Drag a paring knife through the batter 2 or 3 times. Sprinkle with coarse sugar.
- BAKE 50 to 60 min. Cool in pan on rack, about 10 min. Remove from pan and cool on rack completely.
How to melt chocolate using a double-boiler