Making the Crust:
In a large bowl, combine the flour and salt. Add the butter and work it into the flour with your fingertips until the mixture resembles coarse sand.
Add the egg and egg yolk, mixing with your hands until the dough comes together. Avoid overworking the dough. If needed, add a teaspoon of cold water at a time.
Wrap the dough in plastic and refrigerate for 40 minutes.

Making the Filling:
Heat olive oil and butter in a large skillet over medium heat. Add onions and garlic, sautéing until softened and fragrant, about 2 minutes.
Add tomatoes and cook until softened, 2-3 minutes.
Add hearts of palm and olives, stirring to combine.
Stir in flour, cooking for about a minute. Then, add milk and cream cheese, stirring until melted and thickened, about 5 minutes.
Season with salt and pepper, then add chopped parsley. Allow to cool to room temperature before assembling.

Assembling the Hand Pies:
Preheat oven to 350°F (175°C).
Divide the dough into small portions (about 2 tablespoons each). Press each portion into the bottom of an egg tart mold, leaving excess dough hanging off the edges.
Spoon the filling on top, piling it high.
Press another portion of dough into a disk and place it on top of the filling. Pinch the edges together to seal, trimming excess dough with your fingers.
Repeat with the remaining dough and filling to form about 10 hand pies. Place on a baking sheet.
Brush with egg wash and bake for 45-50 minutes, or until golden brown.

Serving:
Serve the hand pies warm or at room temperature.