To begin, preheat your oven to 190°C (375°F). Grease a large baking dish (around 30 x 20 cm) lightly with oil or butter. Move on to preparing the filling.
In a large bowl, crumble the feta cheese. Add cottage cheese, yoghurt, eggs, sunflower oil, sparkling water, and salt. Mix until creamy but still slightly textured. Transition to preparing the phyllo.
Unroll the phyllo sheets and cover with a damp kitchen towel to prevent drying out. This keeps the pastry pliable while working. Move to layering the base.
Place two sheets of phyllo into the greased dish, brushing lightly with melted butter or oil. This forms the crisp foundation. Proceed to the filling.
Spoon several tablespoons of the cheese mixture onto the phyllo. Tear another sheet into rough pieces, dip into the cheese mixture, and layer loosely across the dish. Continue alternating phyllo and filling until all ingredients are used.
Top the pie with two intact sheets of phyllo. Brush generously with melted butter or oil to achieve a golden finish. Move to baking.
Bake for 40–45 minutes until the surface is deep golden brown and crisp. If the top browns too quickly, cover loosely with foil. Proceed to cooling.
Allow the Gibanica to cool for at least 15 minutes before cutting. This helps the filling set while keeping the crust flaky. Transition to serving.
Cut into squares or rustic wedges. Serve warm with plain yoghurt or a fresh salad for a complete meal. Presentation tip: Gibanica is traditionally enjoyed straight from the pan at the table, shared among family and friends.