Place the chicken, oil and fajita seasoning in a large zip top bag. Massage the seasoning into the meat to evenly coat it and place into the refrigerator for at least one hour.
In a food processor or blender, add in ranch dressing, jalapeños and cilantro. Puree until smooth. Put sauce into a lidded container and pop it into the refrigerator to chill.
Preheat a grill over medium-high heat. Place the chicken on the grill (discarding the marinade.) Flip after about 5 minutes. Continue to cook for an additional 4-5 minutes (or until cooked through.) Remove from the grill and allow to rest for 5 minutes then shred into bite-sized pieces.
Place the Bush's beans in the food processor and puree until smooth. Pour the beans into a small nonstick pot over medium low heat. Cook the beans, stirring frequently for about 10 minutes until thickened and heated through.
To prepare tostadas: Spread a couple of tablespoons of the beans onto each tostada shell. Top with lettuce, chicken, cheese and tomatoes. Then drizzle with cilantro ranch sauce. Serve immediately.
These would make great soft tacos! Also, boneless, skinless chicken breasts would work for this too!
To make this low carb, serve on lettuce instead of tostada shells.