Sweat onions in olive oil till soft, about 5 minutes.
Add ground beef and break up. Sauté till cooked through, but not browned. Stir in tomato paste and cook for a couple of minutes. Stir in the remaining ingredients, combine well, season with salt and pepper, taste, adjust if necessary. Allow to cool before filling shells
Brush a cookie sheet with cold water, or line with a Silpat baking sheet. Working with one shell at a time (keep the rest covered so they don’t dry out), put about a tablespoon of the filling into the middle of the shell, making sure not to fill too much. Dip your finger in some water and moisten the outer edges of the shell. Fold circle over to make a half-moon shape. Press the edges closed, pressing out all of the air in the empanada. Pinch and twist the edges of the dough into a braid all the way around the edge. Place on cookie sheet. Brush each empanada with egg wash.
Bake for about 20-30 minutes, until golden brown. Serve hot, or at room temperature.