This famous, hearty Irish bread gets its rise from soda—but not the kind you drink!
Adjust oven rack to lower-middle position and heat oven to 400 degrees. Line rimmed baking sheet with parchment paper.
In large bowl, whisk all-purpose flour, whole-wheat flour, wheat germ, sugar, salt, baking powder, and baking soda until combined.
In liquid measuring cup, use fork to stir buttermilk and melted butter until butter forms small clumps.
Add buttermilk mixture to bowl with flour mixture. Use rubber spatula to stir until dough comes together.
Sprinkle clean counter lightly with extra flour. Transfer dough to counter and use your floured hands to knead until smooth ball forms, about 30 seconds.
Pat and shape dough into 7-inch circle. Use paring knife to cut cross into top of loaf.
Transfer loaf to baking sheet. Place baking sheet in oven and bake until skewer inserted in center of bread comes out clean, 45 to 50 minutes.
Baking soda and baking powder are white powders used in almost every baking recipe. When activated, they produce carbon dioxide—a tasteless gas that causes batters and doughs to rise. Unless you like flat pancakes and squat biscuits, don’t leave out the baking powder and soda!
Baking soda is activated when it’s mixed with a moist, acidic ingredient such as buttermilk. Baking powder is activated by any liquid. Many recipes contain both leaveners to ensure maximum rise and good browning (baking soda helps with browning, but baking powder doesn’t).