Heat olive oil in a large skillet over medium-high heat. Sear chicken thighs skin-side down until golden brown, about 5 minutes. Flip and cook 3-4 minutes more.
Remove chicken from the skillet and set aside.
In the same skillet, sauté the red onion and garlic until softened, about 3-4 minutes.
Add sun-dried tomatoes, chicken broth, and Italian seasoning. Bring to a simmer.
Reduce heat to medium and stir in heavy cream and half of the parmesan cheese. Cook until the sauce thickens, about 5-7 minutes.
Place chicken back into the skillet, spoon the sauce over it, and simmer gently for 3-4 minutes until the chicken is fully cooked and the flavors meld.
Adjust seasoning with salt and pepper. Garnish with remaining parmesan and serve.