Preheat your oven to 375°F (190°C) and lightly grease a small oven-safe ramekin or baking dish with a tiny bit of olive oil.
Finely dice the chicken breast into small, pea-sized pieces to ensure it incorporates evenly into the filling.
Heat a non-stick skillet over medium heat with half of the olive oil, then sauté the diced onion and minced garlic until soft and fragrant.
Add the diced chicken to the skillet and cook until opaque, then stir in the fresh spinach and cook just until wilted.
Remove the mixture from heat and let it cool slightly before stirring in the sea salt, black pepper, dried oregano, and fresh dill.
In a medium bowl, whisk the egg and then fold in the crumbled feta cheese and the cooled chicken and spinach mixture.
Lay out one sheet of phyllo dough, fold it to fit the bottom of your dish, and brush very lightly with the remaining olive oil.
Spread the spinach and chicken filling evenly over the first layer of phyllo.
Top with the second sheet of phyllo dough, folded to fit, and brush the top with the last bit of olive oil to ensure a golden finish.
Use a sharp knife to score the top layer of phyllo into squares, then bake for 25 to 30 minutes until the pastry is puffed and golden brown.