Boil a large pot of salted water for the pasta.
Cook the spaghetti or linguine according to package instructions until al dente.
While the pasta cooks, heat a skillet over medium heat.
Add sliced cooked chicken to the skillet, seasoning with salt and pepper.
Sauté the chicken for about 3-4 minutes until heated through.
Drain the pasta, reserving 1/2 cup of the cooking water.
Add the cooked pasta to the skillet with chicken.
Stir in the basil pesto, mixing well to coat the pasta evenly.
If the sauce is too thick, add reserved pasta water a little at a time.
Serve hot, topped with grated Parmesan and pine nuts, if desired.