Preheat your grill or stovetop grill pan over medium-high heat.

Season the flank steak with olive oil, salt, and pepper.

Grill the steak for about 4-5 minutes on each side for medium-rare, or until it reaches your desired doneness.

Remove from the grill and let it rest for 5 minutes before slicing.

While the steak is resting, prepare the green sauce by combining parsley, cilantro, garlic, red wine vinegar, red pepper flakes, and 1/4 cup olive oil in a food processor. Blend until smooth and adjust seasoning with salt and pepper to taste.

Peel and chop the sweet potatoes into chunks and place them in a pot of boiling salted water. Cook for about 15-20 minutes, or until tender.

Drain the sweet potatoes and return them to the pot. Add milk, butter, cinnamon, and salt, then mash until smooth and creamy.

Slice the rested steak against the grain and serve it topped with the green sauce alongside a generous scoop of mashed sweet potatoes.