Pat chicken thighs dry and season with garlic powder, onion powder, salt and pepper.
Heat oil in a large skillet over medium-high heat. Add chicken and sear 4-5 minutes per side, until golden brown and fully cooked. Remove and set aside.
In the same skillet, reduce heat to medium. Add butter and garlic, sauteing until fragrant (about 30 seconds).
Stir in chicken broth and Dijon mustard, scraping up any browned bits.
Add lemon juice, heavy cream, Parmesan, and Italian seasoning. Simmer 2-3 minutes, stirring until smooth and slightly thickened.
Return the chicken thighs to the pan and spoon the sauce over the top.
Simmer for another 2-3 minutes until the sauce coats the chicken well.