- Bring filet mignons to room temperature. 
- Preheat oven to 425°F. 
- Preheat cast-iron skillet over high heat. Season filet mignons with kosher salt and freshly ground black pepper on all sides.
 
 
- Add avocado oil to cast-iron skillet and sear filet mignons on both sides, 3 minutes per side.
 
 
- Add butter and rosemary to pan, and spoon herb butter over filet mignons for 30 seconds.
 
 
- Remove filet mignons from cast-iron skillet and set aside, reserving 2 Tbsp of the pan juices.
 
 
- Place carrot coins and smashed garlic into cast-iron skillet and simmer for 2 minutes.
 
 
- Add 1 Tbsp sherry vinegar and place cast-iron skillet into oven for 20 minutes or until carrots are fairly tender.
 
 
- Place filet mignons back in cast-iron skillet on top of carrots, and cook in oven for 10 more minutes until medium-rare, or meat thermometer inserted into thickest part of filet mignon reads 120°F.
 
 
- Remove cast-iron skillet from oven. Set filet mignons aside to rest, place carrots in bowl and smash. Season with additional kosher salt and freshly ground black pepper as needed.
 
 
- Place cast-iron skillet back on stove over medium heat. Add Brussels sprouts and peas to cast-iron skillet, then add remaining sherry vinegar and sauté for 3 minutes. Season with salt and pepper to taste.
 
 
- Individually plate filet with vegetables or serve family style.  Drizzle remaining brown butter on each plate or over the filets if serving family style.