Heat olive oil in a pan over medium heat. Add chicken breasts and cook for 7-10 minutes until golden brown. Once cooked, let the chicken cool and chop it coarsely.

In the same pan, sauté the chopped onion until caramelized in the chicken drippings, about 5 minutes. Add in the bell peppers and spring onion, cooking until softened. Stir in flour, then gradually add milk, cooking until thick. Remove from heat and mix in the egg, parsley, chicken, and cheese until well combined.

In a mixing bowl, combine flour, salt, vinegar, olive oil, and lukewarm water. Knead until a soft dough forms, then cover and let it rest for 15-20 minutes.

Divide the dough on a floured surface into four equal pieces. Roll each piece out very thinly, dusting with flour to prevent sticking.

Grease a round baking pan with olive oil. Layer some phyllo sheets in the pan, brushing oil between each layer. Spoon the chicken filling in, add more phyllo on top, seal the edges well, and brush the top with oil.

Preheat your oven to 220°C (428°F). Bake the pie for approximately 35 minutes until the top is golden brown. Let it cool for 30 minutes before serving.