Heat olive oil in your large skillet over medium-high heat. Add the bite-sized chicken thighs, seasoned lightly with salt and pepper, and cook until browned on all sides and cooked through, about 5-7 minutes. Remove the chicken from the pan and set aside.
Reduce heat to medium and add the minced garlic and red pepper flakes to the same skillet. Sauté until fragrant, about 1 minute, being careful not to burn the garlic. Pour in the diced tomatoes (with their juices), chicken broth, kalamata olives, capers, and dried oregano. Stir to combine.
Break the spaghetti in half and add it directly to the skillet, submerging it in the sauce. Bring the mixture to a simmer, cover, and cook, stirring occasionally, until the pasta is tender and has absorbed most of the liquid, about 12-15 minutes. Add a splash of extra broth or water if the pasta needs more liquid to cook evenly.
Once the pasta is al dente and the sauce has thickened slightly, return the cooked chicken to the pan. Stir everything together and cook for an additional 2-3 minutes to heat the chicken through and marry the flavors.
Remove from heat and sprinkle with fresh basil leaves and grated parmesan cheese if using. Serve immediately and enjoy the vibrant, savory flavors.
