In a large bowl beat the eggs, then add the Gozo cheese, crumbled feta and mix well. Add in the sour cream, milk, sparkling water, dill and season to taste with salt and pepper. Place the butter in a saucepan and melt. Add in the oil and mix together well. Place 2 sheets of filo pastry in a greased oven dish. Brush the surface with the oil/butter mixture. Crumble a sheet of filo pastry and dip it in the cheese/egg mixture. Place it in the dish and continue with this method until you cover the whole dish. Add any remaining mixture on top of them. Cover everything with 2-3 layers of filo pastry brushing them with the oil/butter mixture. Brush the surface and bake in a preheated oven at 200°c for 30-35 minutes or until golden brown.