Bring a large pot of salted water to a boil over high heat. Add two sprigs of fresh thyme and the rigatoni and cook until tender, but firm to bite, about 10 minutes.
While the pasta cooks, toast the nuts and prep the rest of the ingredients.

In a frying pan over medium heat, toast the pine nuts over until fragrant and beginning to brown, about 2 minutes. Transfer the nuts to a small bowl to cool.

• Remove the root end and tough green portion of the leek. Cut the leek in half lengthwise and then into thin half-moon slices. Rinse and pat dry.
• Chop the garlic.
• Chop the remaining thyme leaves.
• Zest and juice the lemon.
• Crumble the ricotta salata.
• Rinse the beans.

Drain the pasta, reserving 1 cup of the cooking water. Discard the thyme. Add the pasta to the beans with ¼ cup of the reserved cooking water. Add the arugula and toss until wilted, about 2 minutes. If the pasta seems dry, add more of the reserved cooking water. Remove from the heat and stir in the lemon zest, juice and the toasted pine nuts.

Transfer the pasta to two bowls and serve warm. Garnish with the crumbled ricotta salata.