Remove steak from fridge. Let rest 20 minutes.
Pat steaks dry. Season with salt and pepper.
Heat skillet. Add olive oil over medium-high heat.
Step 4: Sear steaks 3 minutes per side for medium-rare.
Transfer to plate. Tent with foil to rest.
Lower heat. Add butter to same skillet.
Sauté shallot and garlic until soft, about 1 minute.
Add mushrooms. Cook until browned, about 4-5 minutes.
Pour in wine. Scrape bottom to deglaze pan.
Add broth, thyme, mustard (optional), and simmer.
Stir in cream (optional) and reduce 2 more minutes.
Return steaks to pan. Spoon sauce over.
Simmer 1-2 minutes to warm through.
Serve hot. Garnish with fresh herbs if desired.