I worked at a Chi-chis all thru college. The hard shell tacos contained beef, cheese, shredded iceberg lettuce, more cheese, tomatoes, and green onions. The cheese was 50/50 shredded Cheddar and Monterrey Jack. The original tacos had shredded beef. The beef was boiled in a steam table with garlic and onions, then allowed to cool and shredded into thin strips. It was then reheated with asada sauce, which was diced white and green onions, some diced green chilies, crushed tomatoes (more for a reddsih brown color than taste), and the corporate spice packet. The spices were unknown, but the asada sauce contained garlic, salt, pepper, msg, and cumin.

1-1/2 of of the beef mixture was then placed in the center of a 6" corn tortilla which had been warmed in a hot fryer. The taco was then folded in half and 2 toothpicks held it shut. When ordered, the tacos could be dropped into a deep fryer. When golden brown (1 minute? 90 seconds?), the line cook would remove the toothpicks and gently tap the taco causing it to open. It could then be assembled.

Hope that helps.