Thinly slice the flank steak against the grain and season with salt, black pepper, and half of the sesame oil. Set aside.

Heat a grill pan over medium-high heat, add vegetable oil. Cook the seasoned steak slices for about 2 minutes per side, then transfer to a plate.

In a large pot, heat remaining sesame oil. Add minced garlic and grated ginger, sauté for 1 minute until fragrant.

Stir in gochujang, gochugaru, soy sauce, and sugar for 1 minute. Pour in chicken stock, increase heat until simmering.

Mix cornstarch with cold water in a bowl to form a slurry. Gradually whisk it into the simmering broth until slightly thickened, about 2 minutes.

Reduce heat to low and stir in the heavy cream. Taste and adjust seasoning if necessary.

Bring water to a boil in a separate pot and cook the ramen noodles as per package instructions, about 3-4 minutes.

Drain the noodles and divide into bowls. Pour the creamy broth over the noodles and top with grilled beef, green onions, sesame seeds, and cilantro.