Whisk the eggs with the salt and sugar. Add the flour and enough milk to make a smooth, fairly thin pancake batter.
Heat a lightly greased frying pan and cook thin pancakes until lightly golden on both sides. Continue until all the batter has been used.
For the filling, combine the cottage cheese with the eggs and sugar. Mix until evenly combined. For a smoother traditional texture, farmer’s cheese or well-drained cottage cheese works particularly well.
Place the pancakes in pairs. Spread the cottage cheese filling between each pair of pancakes.
Cut each filled pancake stack into four pieces.
Grease a baking dish with butter and arrange the filled pancake pieces in the dish.
Whisk together the sour cream, eggs, and sugar.
Pour the sour cream mixture evenly over the pancakes.
Bake at 180°C / 350°F for about 30 minutes, or until the custard is set and the top is lightly golden.
Allow the casserole to rest for 5–10 minutes before serving.