Cook quinoa according to package directions then set aside.
Heat a small skillet over medium-high heat then spray with nonstick spray. Season the chicken breast on both sides with garlic powder, onion powder, salt, and pepper, then saute for 3-4 min per side or until cooked through. Let the chicken breast rest for 10 minutes then chop into bite-sized pieces and set aside.
Heat a medium-sized saucepan over medium heat. Add the flour and 1/2 cup milk then whisk to combine. Whisk in the remaining milk, and green onions then switch to a spatula and turn the heat up slightly to bring the mixture to a simmer, stirring constantly. Turn the heat back down to medium then simmer gently for 1 minute while stirring.
Remove the pan from the heat then add the buffalo sauce and cheddar cheese. Stir until the cheese is smooth and melted then add the cooked quinoa and chicken and stir to combine.
Preheat the broiler. Pour the chicken and quinoa mixture into a nonstick sprayed baking dish then top with chevre. Broil for 5-7 minutes, or until the cheese is golden brown and the sauce is bubbly. Let the dish sit for 15 minutes before scooping into bowls then serving.