Bring water for pasta to a boil.
Heat a large skillet oven medium heat and add bacon. Cook until fat is rendered and bacon is crispy – about 6-7 minutes. Remove with a slotted spoon and place on a paper towel to drain. Reduce heat to low.
Add in leeks with a pinch of salt, then toss mushrooms on top. Stir everything together to coat, then let cook until ingredients are softened – about 5 minutes. At this time, throw the pasta in the water to cook – it is really important that the pasta is hot. While the pasta is cooking, mix eggs and cheese together in a large bowl. The mixture will be thick.
As soon as pasta is finished, reserve 1/2-3/4 cup liquid, drain pasta and immediately throw into the skillet. Toss with the leeks and mushrooms to coat, then remove from heat. With a large spoon in one hand, add the egg mixture right on top and immediately begin stirring the pasta together. I usually stir for a good minute or two. At this time if desired, add the pasta water to the skillet to make things a bit more creamy and saucy. Toss in bacon. Serve immediately with extra cheese!