Start your pasta sauce. Boil a large pot of water or skillet and blanch your peas if they're frozen, cook your peas if they are fresh and once ready and a vibrant green, place in an ice bath and dry when cooled.
In the same pot, pan or skillet as the peas, you’ll begin preparing your sauce. With a drizzle of olive oil on medium heat, heat the pot and toss in your chili flakes (optional), shallots, garlic, leeks, salt and pepper. Sweat out your aromatics for about 3-4 minutes.
Blend your sauce. Next, add in your butter and melt that through, another 4-5 minutes. Transfer your leek mixture to a blender or food processor with your cooled peas, basil, salt, pepper, a drizzle of olive oil and your creme fraiche. Blend until smooth.
Transfer to that same pot or large skillet you had your leek mixture and warm up. At this point, your pasta should be a little bit under al dente.
Add in pasta. First, add in about 1/4th cup of pasta water to the mixture, then slowly drain and add in your pasta. Mix and stir until combined and add in your shredded parmesan cheese, adjusting as you go with cheese and pasta water. Finish seasoning with salt and pepper.
Serve your pasta in a bowl and garnish with freshly cracked black pepper, a hint of fresh lemon juice/lemon zest is optional and fresh basil.