To prep the leeks: discard the top dark green portion of the leeks, keeping the bulbs. Slice the bulbs into rings. Add leeks to a colander and rinse them thoroughly (use your hands to dislodge any stubborn dirt - it may be hidden).
Boil a salted pot of water for the pasta and cook it al dente according to package directions.
Meanwhile, cut the bacon into small pieces (I find this easiest using kitchen shears) and cook in a skillet over medium-high heat until crispy, then transfer the bacon to a paper towel lined plate. Leave the bacon fat in the skillet.
Turn the heat down to medium and cook the leeks for about 3-4 minutes, or until softened (a bit of light browning is ok too - adds more flavor).
Add in the garlic and cook for 30 seconds.
Add in the broth and cook for a few minutes until the liquid is reduced by half (and scrape up any browned bits from the bottom of the pan).
Prior to draining the pasta, reserve 1/4 cup of the hot pasta water and add it to the skillet, along with the parmesan cheese and the bacon. Turn the heat off and add the drained pasta to the skillet and keep tossing it all together until the cheese melts and the sauce thickens up a bit and coats the pasta. I like to add some freshly cracked pepper (add salt if needed, but I found it plenty salty). Serve immediately.