1. **Prepare the crust:**

– In a large bowl, combine the flour and baking powder. Add a pinch of salt.

– Cut in the cold butter using a pastry cutter or your fingers until the mixture resembles coarse crumbs.

– Add the egg yolk and mix to combine. Gradually add cold water, one tablespoon at a time, mixing until a dough forms.

– Divide the dough into two portions, one slightly larger than the other. Wrap in plastic wrap and refrigerate for at least 30 minutes.

2. **Prepare the filling:**

– Heat olive oil in a skillet over medium heat. Sauté the onion and garlic until translucent, about 3-4 minutes.

– Add the bell pepper and cook for another 2 minutes.

– In a large bowl, combine the shredded chicken, sautéed vegetables, corn, olives, hearts of palm, tomato, cream cheese, and mozzarella. Season with salt and pepper to taste. Mix until well combined.

3. **Assemble the pie:**

– Preheat the oven to 375°F (190°C).

– On a lightly floured surface, roll out the larger portion of dough to fit a 9-inch pie dish, including sides.

– Transfer the rolled dough to the pie dish, pressing gently to fit. Trim any excess.

– Spoon the filling into the crust, spreading evenly.

– Roll out the smaller portion of dough and place over the filling. Trim excess and crimp edges to seal. Cut small slits on top to allow steam to escape.

– Brush the top crust with the beaten egg.

4. **Bake:**

– Bake in the preheated oven for 45-50 minutes, or until the crust is golden brown.

– Let the pie rest for 10 minutes before slicing and serving.