Place thawed spinach in a clean tea towel and wring thoroughly to squeeze out as much liquid as possible.

Peel and finely dice the onion and garlic. Add a teaspoon of oil to a pan, add the diced onion and garlic, and sauté with a pinch of salt until the onions are translucent. Meanwhile, wash, pat dry, and finely chop the dill.

Whisk the eggs in a large bowl. Add the spinach and the sautéed diced onion and garlic. Crumble the feta cheese with your hands and add it to the spinach and egg mixture along with the dill, then stir well. Season generously with salt and pepper.

Preheat oven to 200°C (390°F) using conventional oven setting (top and bottom heat). Pour oil and milk into a small bowl so you can dip your brush in it. Grease the springform pan with a little oil or butter.

Now place a sheet of filo pastry in front of you and brush it with the oil and milk mixture. Spread about one-fifth of the spinach filling onto the bottom third of the pastry and roll it up into a long, thin roll. Place the roll in the center of the springform pan, spiraling it like a snail shell.

Repeat the process for the remaining filo sheets, wrapping them around the first roll until the springform pan is filled.

Brush the finished, rolled filo pastries with the remaining oil and milk mixture and sprinkle with sesame seeds, if desired. Bake the spanakopita at 200°C for 20 minutes, until the spinach strudel has a beautiful golden-brown surface.