Bring a 4 qt pot of water to a boil, and salt generously.
Add the garlic, walnuts, and salt to the food processor. Pulse until uniform in texture, occasionally scraping down the sides of the bowl.
While preparing the broccoli rabe, bring another 4-6 qt pot of water to a boil, and salt generously. Add the pasta, and cook according to the box directions (mine was 10 minutes).
Meanwhile, add the olive oil to a 12" non-stick sauté pan and place over medium-low heat. Add the leeks, and sauté until they start to brown. At this point, if the pasta is not yet done, turn the heat down low on the leeks until the pasta is ready.