Preheat your oven to 180°C/355°F, ensuring both top and bottom heating elements are working. This temperature is ideal for cooking the chicken evenly.
Heat a pan over medium heat and add a drizzle of olive oil. Once hot, sauté the onion for about 3 to 4 minutes until it starts to caramelize. This process brings out the natural sweetness of the onion.
Next, add the spinach, dill, mint, parsley, and green onion to the pan. Sauté for an additional 2 to 3 minutes until the spinach has wilted and the herbs are fragrant.
Incorporate the feta cheese, salt, and pepper into the mixture. Stir and cook for about 5 minutes, allowing the flavors to meld. Once done, transfer the filling to a strainer to cool and drain any excess liquid.
On a clean work surface, lay out the deboned chicken. Brush it with a bit more olive oil and season with salt and pepper. Spread the filling evenly over the surface of the chicken, making sure to cover it entirely.
Carefully roll the chicken tightly, ensuring the filling stays in place. Tie it with kitchen twine at five points to secure it. If the chicken is uneven in thickness, gently pound the thicker areas with a meat mallet to help flatten them for a more even roll.
Heat a large pan over high heat and sear the roulade for about 1 minute on all sides until it’s well browned. This step adds a beautiful crust and depth of flavor.
Transfer the roulade to a baking tray lined with parchment paper. Cover it first with parchment paper and then with aluminum foil to keep it moist during baking. Bake for 1½ hours.
After 1½ hours, uncover the roulade and bake for an additional 20 to 30 minutes, or until it turns golden brown. This final step crisps up the outside.
Once cooked, let the roulade rest for about 10 minutes. Remove the twine, slice into portions, and serve with mashed or roasted potatoes for a complete meal.