Using a whisk or a fork, mix 3 eggs, the oil, the baking soda, and the yogurt in a medium-sized bowl.

Add the crumbled feta cheese to the egg-yogurt mixture.

On each filo sheet, add some of the egg-cheese mixture. If using our measurements and a 9-inch pan, then use about 1/6 of the egg-cheese mixture on each filo dough sheet.

Add tiny cubes of butter on each filo dough sheet. Again, if using our measurements, you’ll be using 1/6 of the butter on each filo sheet. Take the short edge of the filo dough, and roll each sheet (as shown below).

In the round baking pan (which should be either lined with baking paper or greased with some oil or melted butter so the filo dough doesn’t stick to the bottom), add each rolled sheet like a spiral (as shown below). Repeat with each rolled filo dough sheet until the round pan is full (as shown below).

Mix the milk with the remaining egg with a whisk or fork.

Pour the egg and milk mixture over the banitsa.

Poke holes with a fork so that the banitsa absorbs the milk better.

Preheat the oven to 180°C (360°F) and place the banitsa in the oven for about 50 minutes. Place it on a lower level so it doesn’t burn the top. Once ready, your banitsa should have a beautiful golden brown crusted exterior, and is ready to serve to your family or dinner guests.