In a medium saucepan, whisk together chicken broth and flour until smooth. Cook over high heat for 1 minute. Add the milk and seasoning and cook for 3-5 minutes until thickened.
Cut up sweet potato and chicken into small bite size pieces. Chop leeks into small pieces.
In a large bowl, combine the sauce with the quinoa, chicken, leeks, sweet potato, and pesto. Pour into a 9x13 baking dish. Top with shredded cheese and bake for 40-50 minutes covered, until the quinoa is soft and the chicken and sweet potatoes are cooked through.