Heat the butter in a skillet just wide enough to hold the fish. When hot add the vegetables and saute for a minute or so just to get them sizzling. Add the wine, cover and cook over very low heat until wilted, about 10 minutes.
Set halibut over the vegetables, season with salt and pepper and add stock or broth just to cover. Simmer, covered, over low heat, until fish is just done, about 10 minutes.
With a slotted spatula, remove haibut from the liquid and divide into two portions. Set each portion in the bottom of a deep soup plate and garnish with carrot threads or snow peas; season the broth and spoon it over the top; garnish with black sesame seeds if you wish.