While the pasta is cooking, let's also start on the bacon. Cut the bacon into 1-2" strips. Place the strips in a skillet and cook over medium heat until the bacon is done. Stir occasionally. 10-15 minutes.
While the bacon is cooking, clean the mushrooms either by brushing them clean or rinsing them, depending on your preference. Cut off the very end of the ends, then quarter each mushroom.
Remove the bacon from the skillet and place it on a paper towel to drain off the excess grease.
Reserve 1/4 cup of bacon grease. Leave the rest of the grease in the skillet.
To the skillet with the bacon grease, add the mushrooms. Cook over low heat until the mushrooms are cooked, tender, and browned. Remove them from the grease and place them on a paper towel to drain off the excess grease. 5-6 minutes.
Reserve 1 cup of pasta water. Don't drain the pasta yet.