Preheat the oven to 375°F (190°C).
Using a sharp knife, cut a pocket into each chicken breast without slicing all the way through.
In a bowl, combine ricotta cheese, lightly mashed blackberries, Parmesan cheese, garlic powder, salt, and black pepper. Mix until well combined.
Spoon the ricotta mixture into each chicken breast pocket. Secure with toothpicks if needed to keep the filling inside.
Heat olive oil and butter in an oven-safe skillet over medium heat.
Sear the stuffed chicken breasts for 3–4 minutes per side until golden brown.
Transfer the skillet to the oven and bake for 18–20 minutes, or until the chicken is fully cooked and reaches 165°F internally.
In a small saucepan, combine balsamic vinegar, honey, and chicken broth.
Simmer the mixture for 4–5 minutes until slightly thickened, then stir in the fresh thyme.
Remove the chicken from the oven and drizzle the honey balsamic glaze over the top before serving.
