Crush the korean pear, onion, garlic, and ginger with a blender and process until smooth. Transfer it to a mixing bowl, then add soy sauce, sesame oil, brown sugar, red pepper flakes, and black pepper. Stir until well combine and the brown sugar is dissolved. Set aside.
In a pot, bring a water to boil over medium heat. Add noodle and cook for 3 minutes, stirring occasoinally. Remove noodle from heat and strain, then set aside.
In a pan, heat oil and cook onion until fragrant. Add green onion and beef and cook until the beef is half cooked, add bokcoy and cook for 4 minutes.
Add cooked ramen and bulgogi sauce, then mixing all together until well combine. Turn off heat, and transfer the beef bulgogi ramen to a plate, then garnish it with sesame seeds. Enjoy!