Fill a large pot with salted water. Bring to a boil on medium-high heat. Add the spaghetti to the pot and stir. If you are using frozen veggies, carefully add them to the water. Lower heat to medium and cook the spaghetti to al-dente,
Meanwhile, mix together the garlic, red pepper flakes, parsley and 1/2 teaspoon of salt. Set aside.
While pasta is cooking, heat the olive oil on medium low heat until just getting warm. Add the garlic mixture and mix. Lower the gas to low and heat until garlic pieces are golden brown. Garlic will keep cooking after heat is turned off, so don't overcook. Set oil aside.
Carefully pour 1/2 cup of the pasta water into the cooled but barely warm oil, being careful not to pour it into the oil while the oil is hot.
When pasta is al-dente, drain and put back into the pot. Add the garlic and oil mixture to the pasta. Mix well to combine. Garnish with chopped fresh parsley, if desired. Serve immediately.