Heat the oven to 180ºC (160ºC fan), gas 5.
Place the flour in a bowl and rub in the butter until the mixture resembles fine breadcrumbs.
Add the baking powder and salt and stir in just enough boiling water to make a dough.
Turn onto a floured board and knead for 5 minutes then set aside in an oiled bowl while you make the filling.
Heat the oil in a pan and gently cook the onion until soft but not brown.
Add the garlic and the chile peppers and cook for 2 more minutes then remove the pan from the heat.
Roll out the dough on a floured surface as thinly as possible and line a greased deep pie dish about 20 cm/8 in diameter.
Mix the onion mixture into the beaten eggs with the spinach, chicken and cilantro.
Season with salt and pepper and pour into the pie dish.
Scatter over the cheese and bake in the oven for 30 - 40 minutes or until golden brown.
Let cool a little in the pie dish before turning out.
Serve warm or cold.