Bring a large pot of salted water to a boil and cook pasta according to package directions until al dente. Reserve 1/2 cup of the pasta water and drain the rest.
In a large skillet over medium heat, heat the olive oil. Add garlic and sauté for 30 seconds until fragrant.
Add shredded chicken to the pan and warm through, seasoning with salt, pepper, and red pepper flakes if using.
Stir in the ricotta and Parmesan until melted and smooth. Add reserved pasta water a little at a time to loosen the sauce.
Toss in the cooked pasta and mix everything until coated in the creamy sauce. Adjust seasoning if needed.
Serve hot, topped with chopped parsley and a little extra cheese if you like.