Step 1

Spread chicken thighs on a clean work surface. Pat dry with paper towels and season both sides with salt and pepper. Sprinkle 1/2 of the Italian seasoning all over them.

Step 2

Heat oil in a 12-inch nonstick skillet over medium-high heat. Add chicken thighs and brown for 3 minutes per side. Remove chicken to a plate and keep warm.

Step 3

Add onions to the same skillet and stir up any browned bits from the bottom of the pan. Cook, stirring occasionally, until onions just start to become tender, 3 to 5 minutes. Add mushrooms and cook until they begin to soften, about 4 minutes. Stir in garlic and remaining Italian seasoning. Taste and adjust salt and pepper. Cook and stir for 1 minute.

Step 4

Add chicken broth and return chicken thighs to the skillet. Reduce heat to low, cover, and cook until chicken juices run clear, about 15 minutes. An instant-read thermometer should read 165 degrees F (74 degrees C). Remove chicken to a cutting board and cut into bite-sized pieces.

Step 5

Return chicken to the skillet and increase heat to medium. Add tomatoes and spinach. Cook and stir until tomatoes are heated through and spinach is tender, but still bright green, about 3 minutes.

Step 6

Stir in 1/2 cup heavy cream and balsamic vinegar; bring to a gentle boil. Cook and stir for 3 minutes. If you prefer a creamier sauce, add more cream. Serve with shaved Parmesan cheese.