Cook pasta according to package directions, reserving 1 cup of pasta water to finish the sauce. Add asparagus to the pasta during the last 2 minutes of cooking. Drain and reserve.
Meanwhile, in a large saute pan, heat the olive oil over medium-high heat. Cook the ground chicken, breaking up any lumps, until lightly coloured, about 4 minutes.
Add the leeks and cook, stirring, until soft, about 4 minutes. Stir in the garlic, hot pepper flakes and salt, cook for 1 minute.
Add the cooked pasta and asparagus to pan with chicken and leeks. The mixture may seem dry so add reserved pasta water as needed, about two tablespoons at a time. Finish with lemon zest and toss well.
Serve with grated parmesan cheese.