- Heat the olive oil in a large, deep skillet over medium heat. Add the onions, carrots and celery. Cook for 5 minutes, stirring frequently. 
- Add the garlic and cook 1 minute, stirring frequently. 
- Raise the heat to medium-high, add the ground beef, salt, dried oregano, cumin and black pepper to the skillet. Stir to combine the ingredients well, breaking up any large pieces with a wooden spoon or a spatula as you go. Cook the beef for about 5 minutes until browned, stirring frequently. 
- Add the tomato sauce, water and Worcestershire sauce to the skillet. Stir well to combine. Lower the heat to medium-low and cover. Keep the sauce at a simmer, if it’s boiling too vigorously, lower the heat a bit. Cook the ground beef for 12-15 minutes, or until most of the liquid has cooked out. We don’t want it too saucy. 
- Taste the beef filling and add salt to taste, if needed. 
- Remove the skillet from the heat, uncover and allow the ground beef to cool. Give it a good stir every once in a while so that the steam escapes and it cools a bit faster.