Combine beef broth and dried porcini mushrooms in a small saucepan.

Bring to a boil, then remove from heat, cover, and let steep for 30 minutes.

Remove porcini from broth with a slotted spoon, chop coarsely, and set aside.

Strain the broth through a sieve and set aside.

Heat 1 tbsp vegetable oil and butter in a large skillet over medium-high heat.

Add cremini mushrooms and sauté until browned, stirring often, for 5-6 minutes.

Transfer mushrooms to a bowl.

Season beef strips generously with kosher salt and pepper and dredge in flour.

Add 2 tbsp vegetable oil to the pan and heat over medium-high heat.

Add beef to the pan in a single layer.

Brown each side of the beef for about a minute, working quickly to avoid overcooking.

Remove beef to the bowl with the cremini mushrooms.

Melt remaining butter in the pan over medium-high heat.

Add onion and sauté, scraping up browned bits from the bottom of the pan, until onions begin to brown (4-5 minutes).

Pour in the reserved porcini soaking broth.

Stir in Dijon mustard, Worcestershire sauce, porcini mushrooms, cremini mushrooms, and beef, along with any accumulated juices.

Bring to a simmer, stirring, and cook until the sauce thickens slightly (1-2 minutes).

Reduce heat to low and stir in creme fraiche until incorporated and heated through.

Taste and adjust seasonings.

Serve over cooked noodles and sprinkle with parsley.