Heat a small, dry skillet over medium heat until warm. Add the pistachio nuts, stirring frequently until they begin to toast and become lightly brown (about 3-4 minutes). Be careful to not allow them to burn.
In the bowl of a food processor, place 4 cups arugula, garlic clove, toasted pistachio nuts and olive oil. Process until liquefied, scraping sides of the bowl as necessary. Add salt and pepper to taste. Note: If thinner pesto is desired, add more olive oil.
Serve over freshly made pasta with some chopped pistachio nuts for garnish.