Heat the oil in a large skillet over medium heat. Add the onions, peppers and garlic and saute until translucent, about 5 minutes. Add the tomato paste and stir until well combined, 1 to 2 minutes. Add the beef and break it up so there are no lumps. Add the raisins, wine, oregano, salt, pepper and sugar (if using). Simmer covered over medium heat for 15 to 20 minutes, stirring occasionally until mostly dry. Stir in capers and green olives and adjust the seasoning. Set aside to cool. Combine sugar and water in a small saucepan and bring to a steady simmer for about 5 minutes. Remove from the heat and allow to cool. Preheat the oven to 400 degrees F. Line a large baking sheet with parchment paper or nonstick liner. On a lightly floured surface, roll out the first sheet of pastry to about 1/8-inch thick. Cut out 18 to 20 pastry rounds using a 2 1/2-inch round cutter. Cover each round with beaten egg wash. Add one tablespoon of the filling to the center of each round. Roll out remaining sheet of pastry and cut out an equal amount of pastry rounds. Top each filled round, pressing down the sides to seal. Brush the tops with beaten egg wash. Set in the preheated oven and bake until lightly golden, 20 to 25 minutes.
To glaze, remove the pastelitos from the oven and lightly brush with simple syrup, if using.