To cook the chicken: Heat sesame oil in a large skillet over medium heat. Add in the ground chicken and cook, breaking the large pieces with a wooden spoon, for 7-8 minutes or until no longer pink.
Add in the asparagus and let it cook, stirring occasionally, until vegetables are crisp-tender, 4-5 minutes.
Toast the sesame seeds: Place sesame seeds in a small empty skillet over medium heat. Toast, stirring frequently, for 4-5 minutes or until they turn golden brown. Do not leave the site of it as they can burn easily.
Cook the ramen noodles: Meanwhile to cook the ramen noodles, fill a medium-sized saucepan with water and a tablespoon of salt. Bring to a boil. Add the noodles and cook for 2 minutes. Save ¼ cup of the pasta water and drain the rest.
Make the noodle sauce: While the chicken is cooking, make the peanut butter sauce. To do so, whisk together peanut butter, garlic, ginger, soy sauce, rice vinegar, brown sugar, lime juice, and Sriracha ( if using) in a measuring cup.
Assemble: Right before serving, place the ramen noodles into the skillet with chicken and asparagus. Drizzle it with the peanut butter sauce and add in the chopped scallions. Using kitchen tongs, give it a toss making sure that the noodles are evenly coated with the sauce. If it gets too sticky, drizzle it with the reserved pasta water as you toss.
Divide the noodles into bowls and garnish with chopped peanuts, sesame seeds, wedges of lime, and chopped fresh cilantro, if using.