Preheat your oven to 350 degrees Fahrenheit (175 degrees Celsius). Lightly spray a 9-by-13-inch baking dish or a similarly sized casserole dish with non-stick cooking spray. The size of the dish matters here: a dish that is too small will cause the noodles to pile up too thickly and cook unevenly, while a dish that is too large may cause the liquid to evaporate before the noodles have fully cooked. A standard 9-by-13-inch dish is the right size for this quantity of ingredients.
Step 2: Mix the Gravy and Broth
In a large bowl or measuring cup, whisk together the entire can of sausage gravy and the two cups of chicken broth until well combined. The mixture will look thin — considerably thinner than the gravy from the can — and this is exactly right. The liquid needs to be loose enough to fully surround and submerge the dry noodles during baking. As the noodles cook, they will absorb a significant portion of the liquid and release starch that thickens the remaining sauce back to a proper gravy consistency. If the finished sauce looks too thick for your taste when the casserole comes out of the oven, stir in a small splash of warm broth or water before serving to loosen it slightly.
Step 3: Assemble the Casserole
Spread the uncooked egg noodles in an even layer in the prepared baking dish. Pour the gravy-broth mixture evenly over the noodles, making sure every noodle is submerged or at least thoroughly coated with liquid. Use the back of a spoon to gently press any noodles that are sitting above the liquid surface down into the sauce. Every noodle needs contact with the liquid in order to cook through properly during baking — noodles that sit dry on top of the liquid may remain crunchy in the center even after the surrounding noodles are fully cooked.
Step 4: Cover Tightly and Bake
Cover the baking dish very tightly with aluminum foil — press the edges firmly against the sides of the dish to create a seal that will trap steam inside during baking. This trapped steam is essential to cooking the noodles properly: without it, the liquid will evaporate too quickly and the noodles on the outer edges of the dish may dry out before the center noodles have cooked through. Place the covered dish in the preheated oven and bake for 30 to 35 minutes. At the 30-minute mark, carefully lift a corner of the foil (steam will escape, so keep your hand and face away from the opening) and test a noodle from the center of the dish by pressing it with a fork or taking a bite. It should be fully tender with no remaining crunch. If the noodles are still firm, re-cover and bake for an additional 5 to 10 minutes before checking again.
