Nana's Hachapuri from: Nigella Lawson's Feast
Yield: 10 servings (NOTE: Makes a gargantuan outload, so halving is recommended unless you're feeding an army)
Notes: A possible variation that I learned from Wolfert's book, and one which I intend to try next time, is to substitute equal weights of feta and fresh mozzarella for the three cheeses Nigella suggests. This apparently more closely resembles the highly-regarded hachapuri from Mingrelia, in Western Georgia, which is made with the coveted suluguni cheese.

for dough:
about 5 1/2 cups (700g) all-purpose flour (I ended up using quite a bit more)
2 cups (500g) plain whole-milk yogurt
2 eggs
4 tablespoons (50g) butter, softened
1 teaspoon salt
2 teaspoons baking soda

for filling:
7 oz (200g) ricotta cheese
7 oz (200g) fresh mozzarella (preferably buffalo milk mozzarella)
1 lb 5oz (600g or three packages) high-quality feta
1 egg

In a large bowl, stir together the yogurt, eggs, butter and salt. Begin adding the flour, a cupful at a time, stirring or working with your hands to form a silky, soft dough. Add as much flour as is necessary to bring the dough to a kneadable consistency - it should not be overly sticky. Knead in the baking soda. Although Nigella doesn't mention it, I would recommend turning the dough out onto a floured surface and kneading lightly for a few minutes - this activates the gluten in the flour and will make the dough less prone to tearing when you form the breads. Wrap the dough in plastic and refrigerate for at least twenty minutes, or up to a day.

For the filling, chop or mash all the cheeses together in a bowl. Stir in the egg.

Preheat the oven to 425F/220C. You can either make six small hatchapuris or one large one. To make a large one, separate the chilled dough into two equal parts. Roll one of them out on a well-floured surface to a circle approximately 1/4-inch (1/2-cm) thick and transfer it to a baking sheet. Spread the cheese in the center to within an inch of edge. Roll out the second piece of dough in the same manner and place it on top of the cheese. Fold in the edges to seal in the outside of bread, curling them inwards to form a roll of dough. Press down on the roll with the tines of a fork, sealing the two layers together. Transfer the bread to the oven and bake until golden brown, about 20 minutes.

To make smaller hachapuris like I did, divide the dough and the cheese into six equal parts. Using your hands, press each piece of dough out into a rough circle about 8 inches in diameter. I found that it was best to leave the center slightly thicker and concentrate on stretching out the sides, creating a kind of slim flying-saucer shape. Mound a sixth of the cheese into a fat disc in the center and start bringing the sides of the dough up around it, pleating them as you go (you can moisten the pleats with water to create a better seal). You should have a gathering of dough at the top when you finish - twist this around itself to seal. Now pat this cheese-filled dough ball out until it is about 1/2-inch thick. Bake for about 10-15 minutes. You can also cook this bread in a heavy skillet on the stovetop until both sides are golden brown.

Cool the hachapuri slightly to let the cheese set, but eat warm.