Preheat oven to 350 degrees. Spray a 9×13 in baking dish with cooking spray.
In a large saucepan, bring the chicken stock (or water, if you prefer) and quinoa to a boil and cook according to quinoa package specifications. During the last 5 minutes or so, add the broccoli so it will steam.
While the quinoa is cooking, add 1 tablespoon of olive oil to a pan and heat on medium high heat. When hot, add the Panko breadcrumbs and cook, stirring frequently, until browned. Remove from pan.
Add the other tablespoon of olive oil to the pan and heat. Season chicken on both sides with salt and pepper. When oil is hot, add the chicken to the pan, cooking about 3-4 minutes on each side. Remove from pan and let cool a little before dicing into small pieces.
In the same pan, melt the butter over medium heat. Whisk in flour until lightly browned, about 1 minute. Slowly whisk milk it so it doesn’t boil over and continually stir until sauce thickens, about 4 minutes. Stir in quinoa, broccoli, chicken, about 1 cup of the cheese, and Greek yogurt. Season with salt and pepper to taste.
Add the mixture to the baking dish and spread evenly. Top with the remaining cheese. Pop into the over until cheese is melted, about 5 minutes or so.
Serve by topping with the toasted Panko and enjoy!