Pat the chicken breast dry. If you're working with a thick chicken breast, slice it in half lengthwise (with your knife parallel to the cutting board), to create two thin chicken breast halves**. Set aside.
Combine the garlic powder, onion powder, salt, and pepper in a small bowl and mix thoroughly. Season the chicken with the mixture, reserving 1/2 teaspoon to use later in the dip.
Heat the oil in a large non-stick pan over medium heat. Cook the chicken for about 2-4 minutes per side, until browned and cooked through. Remove the pan from the heat, and transfer the chicken to a large bowl to rest for five minutes.
Shred the chicken in the bowl, and return the chicken and any juices from the bowl back to the pan it was cooked in. Set the pan over medium-low heat, and stir the hot sauce and remaining chicken seasoning into the shredded chicken. Cook for 2-3 minutes, stirring occasionally.
Stir in the whipped cream cheese until fully combined.
Stir in the spinach and cook for 3-4 minutes until the spinach has wilted down and mixed into the dip.
Stir in the sour cream and 3/4 cup shredded sharp cheddar until fully combined.
Transfer the dip to an oven-safe bowl and sprinkle with 1/4 cup shredded cheddar. Broil for 2-3 minutes until the top is browned.
Sprinkle with green onions, and serve hot!