200gunsalted butterMelt and let cool before mixing.
500gall-purpose flourAdd gradually; the amount needed may vary with flour absorption. Aim for a soft dough that holds together.
½tspbaking soda
½tspsalt
For the filling
500gchicken breastBoneless and skinless.
400gpotatoes
160gonions
50gunsalted butterCut into small pieces.
saltTo taste.
ground black pepperTo taste.
For rolling and finishing
1eggBeaten, for brushing the pastry.
unsalted butterFor greasing the baking dish.
all-purpose flourFor dusting the work surface and rolling pin.
You will need
Mixing bowl
Rolling pin
24–26 cm round baking dish, about 5 cm deep
Pastry brush
Oven
Food thermometer
Instructions
Make and bake the pie
Mix the kefir, baking soda and salt in a bowl. When small bubbles appear, stir in the cooled melted butter.
Work in the flour gradually, stopping when the dough is smooth, soft and holds together. It can still feel slightly sticky; do not add flour just to make it dry.
Wrap the dough and refrigerate for 60 minutes.
Prepare the filling while the dough chills: peel the onion and potatoes, finely chop the onion and cut the potatoes into thin matchsticks. Use a separate board to cut the chicken into small cubes. Refrigerate the filling ingredients until ready to assemble.
Preheat the oven to 200°C (400°F).
Divide the dough into two portions, about two-thirds and one-third. Dust the work surface and rolling pin lightly with flour, then roll the larger portion about 0.5 cm thick. Fit it into a buttered round baking dish to cover the base and sides, leaving enough pastry at the rim to seal to the top crust.
Fill the pastry with layers of chicken, onion and potatoes, in that order, seasoning each layer with salt and pepper. Scatter the 50 g of butter pieces over the top.
Roll out the smaller portion of dough to cover the filling. Pinch the edges firmly together and cut a steam vent in the centre of the top crust.
Brush the top crust with beaten egg.
Bake for 45–60 minutes, checking from 45 minutes. Look for a golden crust and potatoes that are tender when pierced. Insert a food thermometer through the steam vent into a piece of chicken at the centre; it must reach at least 74°C (165°F). If the crust browns before the filling is cooked, cover loosely with foil and keep baking until both the chicken and potatoes are done, even if they need longer.
Let the pie rest under a clean kitchen towel for about 20 minutes before slicing.
Storage and safety
Put leftover portions in shallow containers and refrigerate within 2 hours, or within 1 hour if the room is hotter than 32°C (90°F). Keep at 4°C (40°F) or below and eat within 4 days. Reheat until the centre reaches 74°C (165°F).