1. Bring a large pot of salted water to a boil and cook the pasta according to package directions. 2. While the pasta boils, place the garlic scapes, walnuts or pine nuts, Parmesan cheese, lemon juice, salt, and black pepper into a food processor. 3. Pulse until finely chopped, then slowly drizzle in the olive oil while the processor is running until a smooth pesto forms. 4. In a large skillet over medium-high heat, sear the chicken pieces until they are cooked through and browned. 5. Drain the pasta once it is tender, reserving a small amount of pasta water. 6. Toss the cooked pasta and chicken together with the garlic scape pesto, adding reserved pasta water as needed to reach the desired consistency. 7. Garnish with red pepper flakes if using and serve warm.