Bring a big pot of water to a boil, add a liberal dose of salt, then cook penne according to package instructions. Drain and set aside.
Meanwhile, in a large skillet, heat 2 tablespoons olive oil to medium. Add garlic and cook, stirring continuously, for 30 seconds until it begins to turn pale golden. Add cherry tomatoes and continue stirring and cooking for 2 – 3 minutes, just until tomatoes start to soften.
Add arugula to the skillet and cook for 30 seconds, then add pasta, mozzarella, and basil pesto. Toss everything together until pasta is warmed through and everything is lightly coated in pesto.
Sprinkle with pine nuts and a pinch of salt, drizzle with more extra-virgin olive oil, and serve, passing more pesto at the table as needed.