In a large pot of salted boiling water, blanch the asparagus for about 2 minutes or until al dente. Remove from the pot and place in cold water. Drain and set aside.
In the same pot of boiling water, cook the pasta until al dente. Drain and oil lightly. Keep 125 ml (1/2 cup) of the cooking water.
Meanwhile, remove the skin from duck legs and chop it. Set aside. Debone the duck legs and shred the meat. Set aside.
In a large non-stick skillet, brown the duck skin in the oil until crisp. Drain the duck cracklings on paper towels.
In the same skillet, soften the onion and garlic. Add oil, as needed. Add the peas, duck meat and asparagus and cook gently for about 3 minutes, stirring constantly. Add the pasta. Toss to combine and heat through.
In a bowl, combine the reserved cooking water, Parmesan cheese, and eggs. Stir this mixture into the hot pasta and coat thoroughly. Remove the skillet from the heat and let stand for about 1 minute or until the pasta absorbs the sauce. Adjust the seasoning. Serve and sprinkle with the duck cracklings and grated Parmesan cheese, if desired.