Bring a large pot of salted water to a rolling boil. Cook the ramen or udon according to package directions. In the last 1–2 minutes, add the quartered bok choy to the pot so it wilts in the same water. Reserve 1/2 cup of the cooking water before draining.

While the water heats, warm the neutral oil in a large deep skillet over medium-high heat. Add the ground turkey, season with the salt and pepper, and cook, breaking it into small crumbles, until browned and no pink remains — about 5–6 minutes. It must reach 165°F internally; lean turkey crumbles fine with no fat to render, so it cooks fast.

Push the turkey to the edges, add the garlic, ginger, and the white parts of the green onions to the center, and cook 1 minute, stirring, until fragrant.

In a small bowl, whisk the sesame paste, soy sauce, rice vinegar, sugar, sesame oil, Sichuan pepper (if using), and 1/4 cup of the hot reserved noodle water until smooth. It will seize up at first, then relax into a creamy sauce as you whisk.

Add the drained noodles and bok choy to the skillet with the turkey. Pour over the sauce, add another splash of reserved noodle water if needed, and toss with tongs until every noodle is glossy and the turkey is evenly coated.

Drizzle with chili oil to taste — 2 tablespoons for gentle heat, 4 for a real kick. Shower with the crushed peanuts and the green onion tops. Serve straight from the skillet, with extra chili oil and peanuts on the side.