In a wok or skillet, heat 1/2 tablespoon oil until very hot. Add garlic and ginger and stir fry until fragrant, around 30 seconds. Add carrots and onions and stir fry for 2–3 minutes until slightly softened. Add vegetable broth and bring to boil. Stir in miso paste. Add bok choy and soba noodles, then lower heat to simmer. Continue to simmer while preparing salmon.
Liberally season salmon with salt and pepper. Heat skillet or cast iron pan on high heat. Add rest of oil. Turn heat to medium and add salmon. Cook 2–3 minutes on all four sides of the fillet, until medium rare. Take salmon out of pan.
Divide soba noodle and miso broth mixture in two bowls and place salmon on top.