Cook fresh ramen or udon noodles according to the package instructions, about 3-4 minutes, then rinse under cold water and set aside.

In a mixing bowl, whisk together gochujang, soy sauce, brown sugar, sesame oil, and minced garlic until smooth. Add water if the mixture seems too thick.

Heat vegetable oil in a large skillet over medium-high heat and cook the boneless chicken thighs for about 6-8 minutes until browned and cooked through.

Pour the prepared gochujang sauce into the skillet and stir to coat the chicken, allowing it to cook for 2-3 minutes until it thickens slightly.

Add the cooked noodles to the skillet and toss gently to coat them in the sauce, heating through for an additional 1-2 minutes.

Transfer noodles to bowls and garnish with chopped scallions and sesame seeds. Serve immediately.