In a large pot, saute the chopped onion and garlic until translucent and aromatic.
Add the chicken broth, Rotel, enchilada sauce, and spices to the pot.
While the broth is heating up, mix together the masa and milk in a smaller bowl. Add it into the broth. Turn the heat up so the mixture begins to boil and thicken slightly.
Turn the heat down and add the frozen corn, black beans, and shredded chicken.
While the soup is cooking, cover the bottom of a skillet with about 1/2-1 inch of vegetable oil and heat over medium heat. Cut the corn tortillas into strips. Once the oil is hot (you can test it by carefully adding one of the tortillas strips - if it bubbles, the oil is ready), carefully add a handful of tortilla strips to the oil. DO NOT OVERCOOK! You want the strips to be a light golden color but not brown. Use a slotted spoon to remove the strips and place them on a paper towel. Add a pinch of salt to the tortilla strips.
To serve, ladle the soup into bowls and top with your choice of toppings - avocado slices, shredded cheese, sour cream, and tortilla strips.