Put the oil, onions, garlic, and spices in a medium skillet, season with salt and cook over medium to medium-low heat, stirring occasionally until tender, about 10 minutes. Increase the heat to medium-high, add the tomatoes, and their juices and boil to thicken, about 2 minutes. Stir in the beef and chicken broth, adjust the heat so the mixture simmers and cook until the beef is cooked through and the mixture thickens, about 15 minutes. Stir in cilantro, taste, and season with salt and pepper as desired. Transfer to a serving bowl and cover.
To make the taco shells: Pour enough frying oil into a small skillet so its about 3/4 of an inch deep; heat over medium to medium-high. Holding 1 edge of a tortilla with tongs, lay the other half in the oil, keeping it flat with a spatula. Cook until crisp, 30 second to 1 minute. Flip the tortilla over and repeat with the other half, holding the first side of the tortilla at an angle to make an open shell, cook for about 1 minute more. Transfer to a paper towel-lined plate to drain.
Put the fixings and meat in individual bowls and the taco shells on a platter. Serve encouraging your diners to build their own tacos, with meat in the shell with fixings on top.
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