Heat olive oil in a large skillet over medium-high heat. Season chicken thighs with salt, pepper, and Italian seasoning.
Cook chicken in the skillet until golden brown on both sides, about 5 minutes per side. Remove from the skillet and set aside.
In the same skillet, add minced garlic and sauté until fragrant, about 30 seconds.
Pour in chicken broth, scraping up any brown bits from the bottom of the pan. Add half-and-half and bring to a gentle simmer.
Stir in the spinach and cook until wilted, about 2 minutes. Return chicken to the skillet and simmer until cooked through, about 5 more minutes.
Remove from heat and sprinkle with Parmesan cheese. Serve warm, garnished with additional Parmesan if desired.