Combine all-purpose flour, masa harina and salt in the bowl of a food processor and pulse a couple times to mix. Add the cold butter and continue to pulse mixture until it resembles coarse sand, about 5 to 10 more pulses.
In a small bowl, combine the egg, vinegar and three tablespoons of ice water. With the motor is running, slowly add the wet ingredients to the flour and butter mixture and process until a shaggy dough forms, about 30 seconds to a minute (if the dough is a little dry, add more ice water a teaspoon at a time). Turn the dough out onto a lightly floured surface and form into a disk. Wrap in plastic wrap and refrigerate for at least an hour.
While the dough is resting, prepare the filling. In a large skillet, toast the pepitas over medium heat until lightly golden. Add the cumin and one tablespoon of the sesame seeds and continue to toast the seeds and nuts for another 30 seconds, then transfer to a bowl and set aside.
Return the skillet to the stove, add the canola oil and heat over high heat. Add the tomatillos and shallots (cut-side down) as well as the jalapeno and serrano peppers. Cook the vegetables until they are lightly browned and the skin of the peppers are blistered, about 4 to 5 minutes. Add the garlic cloves and continue to cook until it starts to lightly brown, about another minute.
Add the browned vegetables and the reserved toasted seeds and nuts to a blender along with the cilantro, oregano, chicken broth, lime zest and salt. Carefully blend until smooth, taste and adjust seasonings as necessary.
Return the blended mole mixture to the skillet and let simmer over medium low heat for 10 - 15 minutes. Remove from the stove and stir in the shredded turkey or chicken. Set aside.
To make the empanadas, divide the chilled dough into 16 balls. On a lightly floured surface, roll each ball into about a 6-inch round (the rounds should be about a ¼-inch thick).
To form the empanadas, place about 2 - 3 teaspoons of the reserved filling in the center of each round. Fold the dough over, pressing the edges together and finish by pinching little pleats or crimping the edge with a fork. Place the finished empanadas on a parchment-lined baking sheet, about a ½-inch to an inch apart.
Place the baking sheet in the freezer for about 15 - 20 minutes (this will ensure the pastry is nice and flaky). While the empanadas are chilling, preheat the oven to 400°F.
In a small bowl, beat the egg with a teaspoon of water. Remove the chilled empanadas from the freezer, brush with the egg wash and garnish with the remaining sesame seeds. Bake until the crust is cooked through and golden brown, about 25 - 30 minutes. Serve warm or at room temperature.