For the dough, in a large bowl, sift together the flour, masa harina, baking powder, and salt. Stir in the melted butter. Gradually add 1/2 cup to 3/4 cup of water, working it in with your hands to incorporate; the dough should be easy to handle and not sticky. If the dough appears to be dry add a bit more water, as needed. Form the dough into a ball, wrap it in plastic, and chill for 30 minutes.
Meanwhile, place a large skillet over medium flame. Add the ground beef, and cook, stirring for 5 minutes, until the meat gets browned. Add the onion and garlic and continue to sauté until the onions sweat and become translucent. Add the diced red pepper, green bell pepper, diced potatoes, and olives. Cook for another five minutes stirring occasionally.
Season the mixture with the spices. Add the Worcestershire sauce, and tomato paste. Mix thoroughly and cook and stir for 5 minutes, until the mixture is soft. Pour in the broth and simmer for 3 minutes. Allow the filling to cool before stuffing the empanadas.
Once the filling has cooled remove the dough from the fridge. Grab some of the dough and roll it in between your hands forming it into a small ball, the size of a golf ball. Place it on a sheet of plastic wrap or a sandwich bag that has been cut at the sides. Using the palm of your hand squish the ball down and form it into a circle about 1/4 thick. Place a spoonful of the filling in the center of the dough circle. Fold in half and close the edges with your fingers. Crimp the sides to as to avoid any spillage during baking. Repeat with the remainder of the dough and filling. Placing the shaped and filled empanadas onto a baking sheet lined with parchment paper.
Meanwhile for the sauce, blend all the ingredients in a food processor or blender until smooth and creamy. Taste and adjust seasonings accordingly. Store in a container in the fridge until ready to use.
Whisk together the egg and water to create the egg wash. Brush each empanada liberally with the wash and bake in a preheated 350°F oven for about 30 minutes, or until golden brown. Serve with creamy cilantro sauce. Enjoy.