To make the dough: In a large bowl, dissolve the yeast in the water. Add the whole-wheat flour, 1 cup at a time, and then add 1 cup of the all-purpose flour. Stir in the same direction until smooth, and then stir another 1 min. If you have time, cover the bowl with plastic and let rest for 30 min.
Stir in the 1 Tbs. salt. Fold in the oil and melted butter or the lamb fat. Gradually add another 3 to 4 cups flour, mixing the dough until it's too stiff to stir. Turn it out onto a lightly floured surface. Wash, dry, and lightly oil the bowl. Knead the dough, letting it absorb as much flour as needed (by keeping the work surface dusted), until it's smooth and elastic but still a little sticky, about 15 min. Put the dough in the oiled bowl, cover with plastic, and let rise in a cool place for 8 hours or overnight. If you're not ready to bake, punch down the dough, put it in a plastic bag, and refrigerate it for up to 3 days.
To shape and bake: About 1-1/4 hours before you want to serve the breads, set an oven rack on an upper middle rung. Put a large baking stone or unglazed quarry tiles on it, leaving a 1-inch gap around the border. Heat the oven to 500°F.
Turn out the dough onto a lightly floured surface and cut it in half. Cover 1 half; cut the other into 6 equal pieces. Shape each piece into a ball, flatten it with a lightly floured palm, and cover it. Cut the remaining dough into 6 equal pieces and flatten them the same way. Let the balls rest for 10 to 15 min. so they're easier to shape.
Melt about 1 Tbs. butter or lamb fat, finely chop the chives, if using, and set them on your work surface, along with a pastry brush and salt. Lightly dust a rimless baking sheet or peel with flour. Follow the shaping photos below. Transfer the dough to the baking stone and prepare the next round, baking it alongside the first.
Roll out two flattened balls to thin 8-inch rounds, alternating between one and the other to give the dough time to relax. Roll out the others, cover them, and let rest for 15 minutes.
Put one dough round on the peel or rimless baking sheet (near the edge), and stamp or prick the center of the round thoroughly with a fork, leaving a 1-inch rim.
Lightly brush all over with melted butter or lamb fat, and sprinkle the center with a generous pinch of salt and finely chopped chives or scallions, if using. Bake as directed in the recipe.
Bake until each bread is well-flecked with gold, 5 to 7 min. Remove with a peel or long-handled spatula and put on a rack to cool for about 5 min. Wrap in a cotton cloth to keep them soft and warm, and repeat with the remaining rounds.