Wrap steak in plastic wrap, and place in the freezer for 45-60 mins. Unwrap and slice across the grain into ¼ inch thick slices.
Combine pear, soy sauce, brown sugar, sesame oil, garlic, ginger and gochujang. In a gallon size Ziploc bag, combine soy sauce mixture and steak; marinate for at least 2 hours to overnight.
Cook steak pieces in skillet over medium-high heat. Cook in a single layer, flipping once, until charred and cooked through, about 2-3 mins per side. Repeat in batches until complete.
Serve immediately over rice, garnished with green onions and sesame seeds.