5 lbs beef tenderloin, sirloin, or ribeye
1 cup sliced into thin 1/2-inch strips
8 oz cremini mushrooms, sliced
1 medium yellow onion, finely diced
3 cloves garlic, minced
3 tbsp butter, 2 tbsp olive oil
5 cups rich beef broth
1 tbsp Worcestershire sauce
1 tbsp Dijon mustard
2 tbsp all-purpose flour
1/2 cup full-fat sour cream (room temperature)
12 oz wide egg noodles, cooked and buttered
2 tbsp fresh chopped parsley, for garnish