In a medium pot, combine the pasta, chicken stock, salt, pepper, red pepper flakes, chicken breast and onion.
Cover the pot, bring to a boil, reduce heat and simmer for 10 minutes, stirring ever 2 or so minutes.
At this point the pasta should be al dente. Stir in the lemon juice and chopped kale
Cook, uncovered for 2-4 more minutes, until kale is wilted
Stir in the goat cheese until melted through. Serve immediately, garnished with pine nuts.