Rub chicken breast with salt.Heat 1 tablespoon olive oil in a saute pan over medium-high heat. Add chicken skin-side down, and cook until just browned, then flip the chicken pieces.To the pan, add the sake (or white wine or water) and cover with a lid. Allow chicken to steam for about 3 minutes. Transfer chicken to a plate.In the same pan, add remaining tablespoon olive oil and onion and cook until tender and lightly colored. Add garlic and dried chili flakes, and sauté until well combined.Add butter and milk to the pan, and reduce heat to medium-low. Simmer for 2 minutes, stirring every once in a while. Do not let liquid boil.Turn off heat and add miso in 3 evenly divided portions, stirring well between each addition.  Make sure there are no chunks of miso in the sauce.Season chicken with salt and pepper and nestle into the pan, stirring to coat with sauce. Simmer uncovered for a few minutes.Add greens of choice to the pan and mix well to combine. Garnish with herbs.