Preheat your oven to 375°F (190°C).
In a small bowl, stir together ricotta cheese, Parmesan cheese, Italian seasoning, and ⅛ teaspoon of salt until smooth. Set aside.
Season the chicken thighs on both sides with garlic powder and a pinch of salt.
Heat olive oil in an oven-proof skillet over medium-high heat. Once hot, place the chicken thighs into the skillet, smooth-side down, and cook for 3-4 minutes, or until browned on the bottom.
Flip the chicken over, then remove the skillet from the heat.
Spoon the ricotta mixture evenly over the tops of the chicken thighs.
Pour marinara sauce on and around the chicken in the skillet.
Bake in the preheated oven for 25 minutes, or until the chicken is fully cooked. An instant-read thermometer inserted into the center should read 165°F (74°C).
Sprinkle shredded mozzarella over the chicken and return to the oven for another 2-3 minutes until the cheese melts.
Garnish with fresh parsley, if desired, and serve hot.