- Stir the walnut halves with the water, molasses and yeast together in the bowl of a stand mixer fitted with the hook attachment or in a large mixing bowl and let this sit for 10 minutes. Add the bread and whole wheat flour and start mixing on low speed or with a wooden spoon if by hand. Once halfway blended, add the butter and salt and if in a mixer, continue to knead on low speed until the dough is smooth and elastic, about 6 minutes. If mixing by hand, stir until it becomes difficult and then turn the dough out onto a wood surface to knead until elastic, about 8 minutes. Transfer the dough to an ungreased bowl, cover the bowl and let rise until doubled, about 90 minutes.
- Preheat the oven to 400°F (200°C) and line a baking tray with parchment paper.
- Turn the dough out onto a lightly floured surface. Knock the dough down and shape it into a ball (a boule), tucking any rough edges as you shape it and rotating it as you tuck under, to create a taut surface. Place the loaf onto the tray, cover with a tea towel and let rest for 30 minutes.
- Brush the surface of the loaf with the whisked egg and use a paring knife to slash the top across in three rows. Place the bread in the oven and immediately reduce the temperature to 350°F (180°C) and bake the bread for about 45 minutes, until it is a rich brown colour and is hollow when you tap the bottom. Cool the bread on a rack for at least 30 minutes before slicing.