Bring a large pot of lightly salted water to a boil. In a large skillet over medium heat, cook pancetta 4 minutes. Remove to a plate with a slotted spoon. Add leeks and garlic; cook 3 minutes. Turn off heat and set aside.
In a bowl, whisk eggs, Pecorino, pepper and salt. Set aside.
Cook linguine in boiling salted water 9 minutes. (Add peas and asparagus to water after 7 minutes.) Drain, reserving 1/2 cup of the pasta water.
Return pan to medium heat. Add linguine, peas, asparagus and pancetta to leeks and garlic. Cook 1 minute, stirring well. Vigorously mix in egg mixture, making sure not to scramble. Stir in reserved pasta water, if needed, and parsley. Serve immediately, garnishing with more Pecorino and pepper, if using. (If pan isn’t large enough, pasta can be tossed in the pot once linguine is drained.)