Heat a skillet over medium heat and add 4 lightly chopped heaping cups of fresh baby spinach. Allow spinach to cook down, then remove from heat and place in bowl; about 4 minutes.
In a small bowl, combine cooked spinach, chopped sun-dried tomatoes, softened cream cheese, minced garlic, parmesan cheese, mozzarella cheese and black pepper; set aside.
In a small bowl, mix paprika, garlic powder, onion powder, Italian seasoning, ground mustard and black pepper.
Slice center of chicken vertically, making sure not to slice all the way through to other side. The filling will be stuffed in the center.
Evenly spread powder mixture on top and bottom of 2 pieces of chicken.
Evenly stuffed the chicken breasts with the filling. Use a couple toothpicks inserted through the chicken to hold it together.
Place chicken in skillet and cook on medium-high heat; about 10-12 minutes a side.
Carefully flip chicken over and cook another 10-13 minutes.
Chicken should reach an internal temperature of 165 degrees F before serving.