• Preheat your oven to 350°F and mist a 9x13-inch baking dish with cooking spray to prevent sticking. Set it aside for later.
• Cook the pasta shells al dente (firm but cooked) according to the package instructions. This will usually take about 10-12 minutes. Be sure to stir the pasta occasionally to prevent sticking. Drain and set aside once done.

Sauce:

• While the pasta is cooking, melt the butter in a medium saucepan over medium heat. Once melted, whisk in the flour until it forms a paste.
• Keep stirring frequently for 1-2 minutes to cook out the raw flour taste but don’t let it brown. Slowly whisk in the milk, a little at a time, to avoid lumps.
• Lower the heat and cook the sauce until it starts to thicken (about 5-7 minutes). Remove from heat and stir in the Parmesan cheese until it’s fully melted, then mix in the ranch seasoning packet.

Assembly:

• In a medium mixing bowl, combine shredded chicken, spinach, cheddar cheese, green onion, and 1/2 cup of the prepared sauce. Stir everything together well. Fill each shell with about a heaping tablespoon of the chicken mixture and place them neatly in the prepared 9x13 pan, open side up.
• Pour the remaining sauce evenly over the filled shells. If you’d like, sprinkle breadcrumbs and crumbled bacon over the top for added crunch and flavor.
• Cover the dish with foil and bake for 25-30 minutes, until heated through.
• Remove the cover and bake an additional 5-10 minutes until the sauce is bubbling and the top is slightly golden.
• Enjoy your delicious stuffed shells!