Add the olive oil to a large, deep nonstick skillet set over medium heat. When hot, add onion and cook for about 2 minutes.
Add garlic and cook for 30 seconds, until fragrant.
Add green beans, penne, arugula, salt and pepper and mix to combine.
Continue to cook, uncovered for about 2 minutes, stirring occasionally, until the arugula is wilted.
Remove from heat, garnish with the fresh basil and nuts, then serve!