Pat the chicken dry with paper towels. Use your fingers or the back of a spoon to gently lift the skin from the breasts, taking care not to tear the skin.
Using a sharp boning knife, insert the tip into the thickest part of the breast and slice inward, parallel to the cutting board, to create a deep pocket into the centers. Be careful not to cut all the way through or pierce the skin.
Spoon about ½ of the filling into each pocket, pressing gently so it fills the entire cavity evenly. Do not over fill. You may not use all of the filling depending on the size of your chicken.
Drizzle the olive oil over the outside of the chicken and under the skin. Sprinkle and rub the seasoning blend evenly on both sides of the chicken and under the skin. Use toothpicks to tightly close the opening, so the filling stays sealed in place during cooking. Pull the skin over the seam so it overlaps slightly, if possible. Some seepage is normal during the roasting process.
Spread 2 tablespoons of softened butter evenly across a small baking sheet. Place the chicken on the prepared baking sheet and bake, breast side up, at 375°F for 35-45 minutes, or until the internal temperature reaches 165°F. Cooking time depends on the size of your chicken.
Meanwhile, melt 4 tablespoons of butter in a small saucepan over medium-low heat. Add 2 cloves minced garlic and cook until fragrant, about 30-60 seconds. Remove butter from heat and stir in 1 teaspoon of lemon juice, parsley and salt and pepper to taste.
Remove the chicken from the oven and transfer to a serving dish. Carefully remove the toothpicks. Pour the lemon butter over the roasted chicken and top with fresh chopped parsley. Allow chicken to rest for 5-10 minutes before slicing.