Cook the Noodles: Bring a large pot of salted water to a boil. Add ramen or udon noodles and cook for 4-6 minutes until tender. Drain and rinse under cold water.

Prepare the Sauce: Whisk together gochujang, soy sauce, brown sugar, sesame oil, and minced garlic in a medium bowl until smooth.

Cook the Chicken: Heat oil in a large skillet over medium-high heat. Add chicken and cook for 6-8 minutes until golden brown and cooked through.

Combine Chicken and Sauce: Reduce heat and add the sauce to the skillet with the chicken. Toss to coat and cook for 2-3 minutes until sauce thickens.

Mix in the Noodles: Add drained noodles to the skillet and toss with chicken and sauce for 1-2 minutes until heated through.

Serve and Garnish: Divide noodles among bowls, garnish with scallions and sesame seeds, and serve warm.