Mix chili powder, paprika, salt, and black pepper in a small bowl. Pat chicken dry and coat evenly with the spice rub on both sides. Let rest at room temperature for 15 minutes.

Heat vegetable oil in a skillet over medium-high heat until shimmering. Sear chicken undisturbed for 5 to 7 minutes per side until deep golden brown and cooked through (165°F internal temperature). Transfer to a cutting board and rest for 5 minutes before slicing into strips.

While the chicken rests, melt butter in a small saucepan over medium heat. Add 2 cloves minced garlic and sauté for 60 seconds until fragrant. Pour in 1/4 cup heavy cream, stir to combine, and simmer gently for 2 to 3 minutes until slightly thickened. Remove from heat and set aside.

In a separate pot, heat sesame oil over medium heat. Add the remaining 2 cloves minced garlic and cook for 30 to 45 seconds until aromatic. Pour in the chicken broth, soy sauce, and 1/4 cup heavy cream. Bring to a gentle simmer and cook for 5 to 7 minutes, stirring occasionally.

Bring a pot of water to a boil and cook ramen noodles according to package instructions, removing about 30 seconds early. Drain and set aside.

Divide the noodles between two bowls. Ladle the hot creamy broth over the noodles. Arrange the sliced spiced chicken on top.

Drizzle the creamy garlic sauce over the chicken and across the surface of each bowl. Garnish with chopped green onions and chili oil if desired. Serve immediately.