Heat oil in a large pan over medium heat. Add in the onions and cook while stirring until the onions start to soften, about 3 to 4 minutes.
Add the ground beef into the pan with the cooked onions. Use a large cooking spoon to breakup the ground beef into smaller pieces.
Mix in the taco seasoning, salt and tomato paste into the ground beef to combine. Next, mix in the water and or beef broth, if mixture appears dry. Thoroughly cook the ground beef until it is no longer pink, about 6 to 8 minutes or longer as needed.
Remove the cooked ground beef mixture from the heat. Set aside to cool.
On a clean work surface, place down a tortilla, add a good portion of shredded mozzarella cheese, about 3 to 4 tablespoons. Next, spoon over some of the cooled beef filling, about 2 tablespoons.
Starting on the end of the tortilla closest to you, tightly roll the tortilla and filling into a log. Transfer to a baking sheet and repeat with remaining tortillas, beef filling and cheese for a total of (14) taquitos.
Heat some oil in a frying pan, about 1/2 cup, over medium heat. In batches, fry the taquitos starting with the seam side down and rotating with kitchen thongs until all sides of the taquitos are toasted and golden brown, about 1 to 2 minutes. Transfer to a wire rack placed over a paper towel lined baking sheet to catch any excess oil.
Serve taquitos immediately while still hot and crispy! Enjoy!