Bring a large pot of generously salted water to a boil and cooked pasta according to package instructions. When there is 2 minutes left in your cooking time, add the peas. Reserve 1 cup of the starchy cooking water and strain.
While pasta cooks, heat a large skillet over medium-high heat and cooked your bacon until crisp. Let strain on a paper towel. Place mint leaves in a mortar and pestle and grind until it’s a wet paste – it will look like it’s one big chuck but it’s actually a bunch of tiny little mint specks that you’ll be able to taste throughout the pasta. Whisk ½ cup of the pasta water and the egg together until combined.
After straining the pasta (it should still be quite hot when you do this or the egg won’t cook properly), dump in the bacon, mint, Parmesan, red pepper flakes, lemon zest + juice and egg/water mixture. Stir constantly until a creamy sauce develops and thin it out with the extra pasta water if need be. Serve immediately and top with lots of fresh ground pepper and extra Parmesan.