Poticza

Equipment: 2 loaf pans (8.5 x 4.5 inches / 21.5 x 11.5 cm), rolling pin.

Dough

1. Heat the milk and butter together in a microwave or in a small pan on the stovetop until the butter is melted and the milk is very warm, but not boiling. Set it aside to cool until it is warm but not uncomfortable to the touch.
2. Combine ¼ cup sugar, 1 tsp salt, 3 cups flour, potato flour (optional), and yeast in a large mixing bowl. Stir the dry ingredients briefly to mix.
3. Stir in the melted butter, warm milk, vanilla extract, and eggs. Using either the dough hook on an electric mixer, a big spoon, or your hands, mix and knead until the dough is smooth and uniform. This is a "slack" (wet) dough, so it will be quite sticky when you start mixing it. It should come together after a couple of minutes.
4. Cover the kneaded dough and put it in a warm place to rise for about an hour. Alternatively, the dough can be brought to this point, placed in a bowl and covered with plastic wrap or a tightly fitting lid, and left in the refrigerator overnight.

Filling

1. Stir together the chopped nuts, nut meal, the remaining 1 cup of sugar, the remaining ⅓ cup of flour, pinch of salt, cinnamon, and the remaining 3 eggs. The mixture will be a thick paste. However, if it's too thick, you won't be able to spread it. This is most likely to happen if you use very finely ground nuts or nut flours. In that case, add another egg. The nut filling can be made in advance, covered, and stored in the refrigerator overnight.

Assembly

1. Line the loaf pans with parchment baking paper, or grease them with butter.
2. Put plastic wrap with a little flour on your work surface. It may be necessary to put down two overlapping pieces of plastic to make a surface that is large enough. Alternatively, for a more old-fashioned approach, flour a large, smooth, thin cotton cloth and use that to line your work surface. Because the dough will be cut after being rolled out and topped with the nut filling, a silicone baking sheet is not a good choice; the blade of the sharp knife or cutter will permanently damage the silicone mat.
3. Roll out the dough into a rectangle that measures 28x14 inches (72x36 cm). It will be quite thin, about ⅛ inch (3 mm) thick, when you're done. Patch any holes and thin spots.
4. Make sure that the dough is not stuck to your work surface. If it is, loosen it, add a little more flour underneath, and re-check the dimensions with a ruler. If there is loose flour on the top of the dough when you have finished rolling it out, you can use a dry pastry brush to brush it off.
5. Spread the nut filling evenly over the dough, from edge to edge. Any gap will change the swirled design that is seen when you cut the loaf after baking. Because the filling is thick (and even stiffer when it is cold), this will take some time. It may help to break up or slice the filling into many small pieces with a dinner knife, and scatter those across the dough, so that you are spreading small bits of paste over small areas, instead of trying to spread one large lump across a large area. Work gently to avoid tearing the dough underneath.
6. Cover the filling with plastic wrap or parchment paper, and run the rolling pin lightly over it again, without further stretching the dough or increasing the size. This helps flatten any thicker lumps of filling and help any bigger chopped nuts attach more securely to the dough.
7. Use a pizza cutter, pastry wheel, or sharp knife to cut the dough in half, so that you have two matching squares.
8. To get the four-swirl design, the dough has to be rolled from two opposite sides towards the middle. Start by folding one edge of the dough—about one inch (2 cm)—on top of the nut filling, and then continue folding or rolling that side towards the middle. Do not stretch the dough or roll it tightly. Traditionally, the log is formed by folding the first edge, lifting the floured cloth underneath it, and then letting the dough roll itself; you are trying to produce the same effect. After you have the first edge partially rolled, switch to the opposite side, and start rolling it towards the first one, so that they meet in the middle with two evenly matched scrolls.
9. Take one end of the resulting rolled log and fold it to the center of the log. Repeat with the other end. Adjust it, overlapping the ends as necessary, so that the folded log fits inside the loaf pan. Place the folded log in the pan, seam side down.
10. Repeat the process of rolling and folding with the other square of filling-covered dough.
11. Place both pans in a warm place to rise for about 90 minutes or more. It should look a little puffy, but it won't double in size. Alternatively, the loaves can be covered tightly with plastic wrap and put in the refrigerator overnight. Bring the cold dough back to room temperature before baking.

Baking

1. Preheat oven to 350 °F (180 °C / gas mark 4 / moderate oven).
2. Bake both loaves at 350 °F (180 °C) for 30 minutes. Then, cover the tops with a loose "tent" of aluminum foil, to prevent the tops from browning too quickly.
3. Bake for about another 15 minutes after tenting (a total of 45 minutes). If you have an instant-read thermometer, the internal temperature should be around 195 °F (90 °C).
4. To serve, slice the cooled loaf into half-inch (1 cm) slices; you should get about 16 slices per loaf. Serve warm or at room temperature with coffee or hot tea. It can be made a day or two in advance.