Bring a large pot of water to a boil, add the salt and pasta.
Cook until "al dente." Check after 10 minutes, pasta may need 1-2 more minutes to cook.
Drain pasta and toss with oil. Let it cool.
Heat the bacon fat, then add the flour and stir to make a roux.
Cook roux for 4-5 minutes until it turns one shade darker.
Add the garlic and black pepper, cook until fragrant (2-3 minutes).
Slowly add the milk and vegetable stock, whisk to form a sauce.
Bring to a boil, then turn down to a simmer, add the salt and Parmesan. Stir and cook for 15-20 minutes to build flavors.
When sauce has reached a silky consistency, turn off heat.
Whisk the egg yolks to combine, then start blending the sauce. Pour in the mixed egg yolks and mix immediately! Don't let the egg yolks sit and cook!
When yolks are blended, transfer sauce to a container for cooling and storage.
Cut the bacon into 1/4" strips.
Spread lardons on a sheet tray and roast at 375F until crispy.
Set up a pan with holes over a regular pan. Transfer cooked bacon lardons to this pan and let drain/dry for 10-15 min. Transfer to the fridge.
Toss the cooked and cooled pasta with the carbonara sauce.
Top with bacon lardons, defrosted peas, chopped parsley, shredded Parmigiano Reggiano, and a sprinkle of coarse ground black pepper.
Serve immediately, enjoy!