1. Put the rack in the middle of the oven and preheat the oven to 350ºF. (180ºC.) Line a sturdy baking sheet with parchment paper or a silicone baking mat and put it on the oven rack.
2. Mix the whole wheat flour and wheat bran or germ in a large bowl.
3. Sift in the white flour mixed with the baking soda and salt. Stir the flours together, to combine.
4. Cut the butter into little bits and rub them into small pieces with the flour mixture using your fingers, until as small as possible.
5. Stir in the buttermilk and molasses until the dough is uniformly damp. Turn out onto a lightly floured countertop and knead not-too-vigorously, until the dough forms a smooth ball. (If making two, divide the dough into two equal-sized pieces and roll each separately.)
6. Use a sharp serrated knife to slice a cross deeply into the top of the bread, about 1-inch (3cm) deep. Place the brown bread loaf on the hot baking sheet, being mindful that the baking pan is hot.
7. Bake for 45 minutes, or until the loaf is firm on top and when you tap the bottom, feels hollow. (If baking smaller loaves, I would begin to check them for doneness after 25 minutes.)
8. Remove from oven and cool on wire rack for one hour.
*For those who can’t get buttermilk, mix 1 part plain whole-milk yogurt with 1 part low-fat or regular milk and let stand for five minutes before using.