Preheat oven to 400°F. Prep a casserole dish with cooking spray.
Microwave potatoes until somewhat tender. Chop into bite sizes pieces. Layer on the bottom of casserole dish.
Add turkey sausage and broccoli to a large skillet. Cook, stirring occasionally on medium heat until sausage is cooked through and broccoli is somewhat tender. Layer on top of potatoes.
In the same skillet, melt butter and add onions. Sauté the onions until soft. Add garlic and stir for one minute. Stir in flour. Add milk and half & half and stir until thickened. Add cheese. Cook over medium heat, stirring occasionally until cheese is completely melted. Stir in black pepper.
Pour cheese mixture over top of the sausage and broccoli and spread evenly.
Bake for 30 minutes covered. Then uncover and continue to bake for an additional 10 minutes.