Preheat the oven to 350 degree F.
Make the béchamel sauce by adding the ghee and flour to a small saucepan. Whisk over medium heat for about 1 minute. Slowly whisk in the coconut milk and bring to boil. Lower the heat and let cook until nice and thick, stirring often. Remove from heat and stir in 1 cup of the Parmesan cheese (save the remaining 1/4 cup for the top of the casserole). Cover and set aside.
Add a little olive oil to a skillet and add the chopped onion. Cook over medium heat for about 5 minutes. Turn up the heat a little and add the ground bison, and a pinch of salt and pepper. Cook until browned and crumbled. There shouldn't be any fat, but drain if necessary. Remove from heat and set aside to cool.
Meanwhile, boil some filtered water and add salt and the pasta. Cook for 5 minutes and then drain.
Mix together the béchamel cheese mixture and 3/4 of the bottle of marinara sauce. Add in the pasta and bison. Stir well and then transfer to a baking dish. Pour the remaining marinara sauce from the jar on top of the casserole and sprinkle with the remaining Parmesan cheese.
Bake for 20 minutes. Then turn the boiler to high and broil the top for about a minute or two. Remove from the oven and then let rest for a few minutes before serving. And most importantly - enjoy!