Heat large saucepan to medium heat. Once hot, add olive oil to pan.
Toss in diced pancetta and cook 3-4 minutes, until barely starting to brown.
Add butter and let melt into pancetta, then add chopped leeks.
Stir and coat all chopped leeks and pancetta evenly in butter, and cook for 7-8 minutes until leeks become soft.
While chopped leeks is cooking, add dried fettuccine noodles to boiling, salted water. Cook only a few minutes until al dente. Remove from heat and drain, but keep about 1/4 cup of salted pasta water in a measuring cup to the side.
In the large sauté pan with leeks and pancetta, pour in heavy cream and turn heat to medium-high. Once simmering, stir the cream sauce around and thoroughly combine with other ingredients. Season with thyme, salt and pepper, then turn heat down to medium-low and let cook for another 3-4 minutes.
Combine al dente pasta noodles with cream sauce and coat evenly. If sauce is too thick, slowly add pasta water until you reach your desired consistency.
Serve hot, and top with freshly grated parmesan!