To caramelize the onions, slice two large onions into thin slices and add to a cast iron pan with 5tablespoons of butter. Let the sweat and begin to render down, stirring frequently.
Lower the flame to a medium low flame, and continue to stir to onions. Caramelized onions give off a very sweet smell and look golden brown, this should take about an hour. Once the onions are fully caramelized, remove the onions from the pan and set aside.
In a large bowl, add the ground chicken, seasoning, breadcrumbs, parmesan, and ½ cup of the caramelized onions, chopped.
Combine the mixture and form meatballs.
Add the meatballs to a sheet pan and bake for 30 minutes at 375º.
One the meatballs are baked, add to a dish and top with caramelized onions.
Top with gruyere cheese and thyme and bake at 350º to melt the cheese, approximately 10 minutes.
Switch the oven to broil for 2-3 minutes or until the cheese is melted. Top over orzo, rice, or pasta.
Notes
Do not over-mix the ground chicken: When mixing, use four fingers and rake the meat into the center of the bowl, mixing as you go. Once the egg, breadcrumbs, and other ingredients are combined, stop mixing!