Preheat oven to 350°
In a large non-stick skillet, saute the ground turkey and onion until there is no longer any pink in the meat. Stir in the jalapenos and taco seasoning and cook for an additional 2 minutes.
Meanwhile, in a skillet over medium heat, melt the butter and whisk in the flour. Continue whisking as you cook for 2 minutes.
Very slowly, add the milk as you continue to whisk vigorously. When all of the milk has been incorporated, stir in the salt and pepper. Fold 1 cup sharp cheddar until it is all melted.
Stir the ground meat and onion mixture into the cheese sauce.
In a separate pan, begin scrambling your eggs over medium-low heat. Once the eggs are almost set, add them to a greased 8x10 baking pan. Top the eggs with the cheese and meat mixture. Top with the remaining 1/2 cup shredded cheese.
Cover and chill overnight.
Bake at 350° for 30 minutes. Allow to rest for 5-10 minutes before serving so it can set up.
(If you aren't chilling the casserole overnight, only bake for 20 minutes)
Serve topped with green onions and salsa.