In a medium mixing bowl, whisk together the beefy onion soup mix, the first 14-ounce can of beef broth, the minced garlic, and the condensed cream of mushroom soup until completely smooth and unified.

Lay your whole chuck roast flat at the bottom of a 6-quart slow cooker. Pour the whisked mushroom soup mixture directly over the top of the meat, making sure the entire surface of the roast is covered in the wet marinade.

Secure the lid tightly and cook on Low for 8 hours (or High for 4 hours). Pro Tip: Using a whole chuck roast on a low temperature allows the tough connective tissues and white lines of intramuscular fat to gently melt into gelatin over time, which infuses the entire broth with a deeply rich mouthfeel.

Once the 8-hour window is complete, carefully remove the lid. The beef should be completely tender. Use two sturdy forks to break the meat apart directly inside the pot, shredding it into bite-sized strands.

Pour the remaining 3 cups of beef broth straight over the shredded meat and stir well to loosen the gravy base. Replace the lid and cook on Low for an additional 3 hours (or High for 1 hour). This second slow simmer forces the shredded beef fibers to absorb the garlic-onion gravy like a sponge.

Exactly 20 minutes before your slow cooker timer ends, bring a separate large pot of salted water to a rolling boil on your stovetop. Cook the egg noodles according to the package directions, but strain them 1 minute early so they retain a firm bite (al dente).

Pour the hot, drained egg noodles directly into the slow cooker with the shredded beef and gravy. Toss gently to coat everything. Put the lid back on and let it simmer on the "Warm" setting for 10 minutes. The starch-starved pasta will quickly absorb the surface juices, locking the gravy onto the noodles without turning the pot gummy. Garnish with fresh parsley before ladling into bowls.