Prepare and cook the Black Beans in stock and water following the on-pack instructions until tender. Set aside with lid on the pot to keep beans warm.
In the meantime, coat chicken pieces in the Mexican seasoning and pan fry chicken until cooked through and golden. Set aside and keep warm.
Coat corn with cooking spray. Grill the cob in an unoiled grill pan (or on the BBQ) turning occasionally until the kernels are charred in spots. Once the corn is cool enough to handle, slice down lengthwise to remove kernels from the cob.
Mash the avocado with sour cream and season with salt and pepper to taste.
To assemble the salad: place cooked Black beans into a large salad bowl, mix through the corn and cherry tomatoes. Top with chicken and avocado mix, garnish with spring onions and serve.