Cook chicken thighs then transfer the cooked chicken to a plate and set aside.
Cook bacon until crispy. Set aside.
Melt butter in the same pan, add onion and cook until transparent and edges are golden. Stir in garlic powder and Italian seasoning.
Pour in chicken broth and lemon juice and, using a wooden spoon, scrape up browned bits from the bottom of pan. Simmer until liquid has reduced by about half.
Stir in heavy cream and Dijon mustard and bring mixture to a simmer before reducing heat and allowing the sauce to thicken.
Stir in shredded Parmesan and allow to melt before stirring in spinach and allowing leaves to wilt.
Return the chicken to the pan, sprinkle on bacon crumbles, and garnish with parsley and pepper.