In a large pot, bring water to a boil over high heat. Add ramen noodles and cook according to package instructions, about 3–4 minutes, until al dente. Drain and reserve ¼ to ½ cup of cooking water.

In a sauté pan, melt butter over low heat. Stir in miso paste, garlic chili paste, honey, and ginger paste. Gradually whisk in reserved noodle water until the sauce is smooth, about 2–3 minutes.

Add the cooked noodles to the pan and toss for about 2 minutes to coat them evenly.

Remove from heat and stir in sliced green onions. Transfer to serving bowls and sprinkle with sesame seeds if desired.