Heat olive oil in a very large skillet over medium heat.
Make sure the bottom of the skillet is totally covered with oil.
Place chicken thighs in skillet.
Brown chicken well on both sides and remove to paper towel-lined platter.
Set aside.
Drizzle more olive oil into skillet.
Add carrots, bell peppers, mushrooms, onion and garlic.
Sauté a few minutes until veggies become tender, about 5-10 minutes.
Add tomato paste, whole tomatoes with about half of the liquid, fire-roasted tomatoes and seasonings to the skillet.
Cut the whole tomatoes up with a fork.
Add about half of the liquid that's in the can from the whole tomatoes.
Cover with lid and simmer about 10 minutes.
Add chicken thighs.
Cover with lid and heat through an additional 15 minutes until chicken is tender.
Serve over cooked, drained, spaghetti that’s been tossed lightly with olive oil.
Garnish with fresh basil, if desired.