1. Combine the water, walnut oil, salt, and sugar. Stir in the whole wheat flour, yeast, then enough of the bread flour to make a dough that is difficult to stir.

2. Knead the dough on a floured surface for 5–8 minutes, adding more flour when necessary, until the dough is smooth and elastic. Shape the dough into a ball.

3. Coat the inside of a large bowl with oil. Add the dough, and turn to coat with oil. Cover with plastic wrap and let stand in a warm place about 1 hour, or until doubled in volume.

4. Punch down the dough, turn it out onto a floured surface, and knead for 1 minute. Pat the dough into a rectangle and sprinkle with the walnuts. Roll the dough, and knead until the nuts are distributed.

5. Lightly flour a large baking sheet. Cut the dough in half and form each into a ball. Transfer to the baking sheet and flatten lightly. Loosely cover with plastic wrap, and let rise for 15 minutes, until puffy.

6. Preheat the oven to 425°F (220°C). Lightly dust the balls of dough with flour. Cut a square, no more than ¼ in (5cm) deep, in the top of each. Bake for 10 minutes. Reduce the temperature to 375°F (190°C) and bake for 25–35 minutes or until the bases sound hollow when tapped. Transfer to a wire rack and cool.