Poach your chicken. Bring a medium pot of water to a boil over high heat. Once boiling, add the chicken breasts so that they are fully submerged in the water. Return to a boil, cover, and remove from heat. Allow chicken to cook for approximately 20-30 minutes, or until internal temperature registers 165 degrees F. Carefully remove the chicken from the pot and, once cool enough to handle, shred using two forks.
Caramelize the onions. As the chicken cooks, prepare the onions. Heat 1 tablespoon of oil in a medium-to-large skillet over medium-high heat. Add the chopped onion and cook, stirring occasionally, for 10-15 minutes. Sprinkle the brown sugar over the onions and continue to cook until brown and caramelized. Remove from heat and set aside.
Preheat oven to 425 degrees F. and grab a large mixing bowl. Add all the ingredients (softened cream cheese, ranch dressing, BBQ sauce, garlic, red bell pepper, green onion, cheeses, corn, caramelized onions, AND, the chicken). Mix well to combine.
Transfer the mixture to a large cast iron or oven-safe skillet (or baking dish). Drizzle the top with additional BBQ sauce and sprinkle with a mixture of cheddar and mozzarella cheese. Bake for approximately 20-25 minutes, or until mixture is bubbly and cheese is golden and melted.
Drizzle with additional BBQ sauce, if desired, and serve with your favorite crackers and chips! Enjoy!