Make the dough: In a large mixing bowl, combine the flour and salt. Gradually add the warm water, oil, and vinegar (if using), and mix until the dough begins to come together. Knead the dough on a floured surface for 10-15 minutes, or until it becomes smooth and elastic. The dough should not be too sticky or too dry, so adjust with more flour or water as needed. Once the dough is kneaded, cover it with a damp cloth or plastic wrap and let it rest for about 30 minutes to allow the gluten to relax, making it easier to roll out.
- Prepare the filling: In a separate bowl, whisk together the eggs, ricotta cheese, sour cream (if using), salt, pepper, and parsley. Stir until the mixture is smooth and well combined. You can also add spinach or sautéed onions to the filling if you prefer extra flavor.
- Roll out the dough: After the dough has rested, divide it into 3 or 4 equal portions. On a floured surface, roll each portion into a thin sheet, as thin as possible without tearing. You can use a rolling pin or your hands to stretch and flatten the dough. Once you have rolled the dough, set it aside on a floured surface and proceed with the next portion.
- Assemble the Gibanica: Preheat your oven to 375°F (190°C). Grease a baking dish with oil or butter. Lay one sheet of dough into the baking dish, letting the edges hang over the sides. Brush with a bit of oil or melted butter. Spoon a layer of the cheese mixture over the dough. Repeat the process of layering dough and cheese mixture until you’ve used up all the ingredients, finishing with a layer of dough on top. Fold any overhanging dough edges over the top layer.
- Bake: Brush the top layer of dough with a bit of oil or melted butter. Place the Gibanica in the preheated oven and bake for 30-40 minutes, or until the top is golden brown and the filling is set. The Gibanica should be crispy on top and soft on the inside.
- Serve: Once baked, remove the Gibanica from the oven and let it cool for a few minutes before slicing. Serve warm or at room temperature, and enjoy it with a dollop of sour cream or a side salad for extra freshness.