Prepare the short ribs by drying them with paper towels and seasoning with kosher salt, pepper, and ground mustard. Lightly coat with all-purpose flour.

Heat canola oil in a large pot over medium-high heat. Sear the short ribs in batches for 4-5 minutes on each side until golden-brown. Set aside.

In the same pot, sauté sliced onions for 5-6 minutes until translucent. Add minced garlic and sauté for an additional 1 minute.

Deglaze the pot with beef broth, scraping the bottom for flavor, and return the seared short ribs. Bring to a gentle simmer and cover.

Let stew on low heat for 2.5 to 3 hours until the ribs are fork-tender.

Remove the short ribs and strain the cooking liquid into a bowl, discarding solids but retaining broth.

Melt butter in the pot and sauté mushrooms for 6-7 minutes. Add cooked onions.

Stir in flour for 1 minute, then gradually whisk in reserved beef broth, bringing to a boil and reducing to a simmer.

Incorporate heavy whipping cream, sour cream, Worcestershire sauce, and Dijon mustard into the sauce, adjusting seasoning as necessary.

Add egg noodles, cooking uncovered for 8-10 minutes or until noodles are tender and sauce thickens.

Serve topped with short ribs and garnish with parsley, chives, or Parmesan cheese, if desired.