Knead, while constantly adding flour, until you get a soft and stretchy dough. Divide it into 8 identical balls, don't wait for them to rise. Roll out each one into a sheet with a 8″ (20 cm) diameter.
Put thin slices of butter on each sheet. Then, place the next sheet, butter, sheet and so on until you've placed them all. Don't put butter on the final sheet. Be careful not to have too much butter near the edges because it'll spill out when you're rolling the whole thing out and it'll ruin it.
Roll out the entire thing into a large, round sheet, about 1/4 thick. Once you've done this, cut it into 2, then 4, 8, up to 16 pizza-like slices, as much as the sheet allows for. At the end of each slice, put chocolate, feta cheese or jam and start rolling them up toward the middle.
Arrange your croissants in an oven dish, with at least a couple inches between them because they fluff up a lot. Leave them to rise for at least 30 min. in a warm area. Then bake in a preheated 356°F (180 °C) oven.