Season fish with salt and pepper. Heat 2 tablespoons of oil in a large skillet over medium-high heat.
Add fish cubes and sauté until barely cooked; remove from skillet and set aside.
Heat remaining oil in the same skillet; add next 4 ingredients (carrots through green onions) and sauté until tender crisp.
Return the fish to the skillet then add the gingerroot.
In a cup, combine broth and cornstarch; add to the skillet and cook and stir until thickened and halibut is heated through and flakes easily when tested with a fork.