Step 1

In medium bowl, mix beef and steak seasoning. In 5-quart Dutch oven, melt 2 tablespoons of the butter over medium-high heat. Add steak in single layer; cook 4 to 7 minutes, turning once, just until browned on both sides. Using tongs, transfer beef to plate; cover with foil and keep warm.

Step 2

Add remaining 2 tablespoons butter to drippings in Dutch oven; melt over medium-high heat. Add mushrooms and onion. Cook 7 to 9 minutes, stirring frequently, until mushrooms brown and onion softens.

Step 3

Stir in broth; heat to simmering. Place sour cream in medium bowl. Using ladle, spoon 1/2 cup simmering liquid into sour cream; beat with whisk to combine. Set aside.

Step 4

Stir noodles into mixture in Dutch oven; heat to boiling. Reduce heat; simmer uncovered 10 to 15 minutes, stirring occasionally, until noodles are cooked through and most of liquid is reduced (mixture will be saucy). Stir in beef and any accumulated liquid; return to simmering. Remove from heat; stir in sour cream mixture. Let stand 5 minutes.

Step 5

Top with parsley.