In a blender or food processor, combine the sunflower seeds and sage and chop until finely ground. Toast lightly in a non-stick skillet on medium high heat until lightly brown and fragrant, continuously moving in the pan. Preheat oven to 375F. Pat the cod dry with a paper towel. Sprinkle on cornstarch and gently pat to distribute evenly. Place on a baking sheet (use a silicon liner; the fish is so tender that it will break if sticks then shrinks when cooking!); sprinkle with salt & pepper sparingly. Drizzle the honey onto one side, gently use the back of a spoon to spread evenly. Pour the seeds and sage on top, ensure that they evenly cover the fish. Drizzle olive oil on top, and bake in the top third of the oven until opaque; 10-12 minutes. Brown under broiler if fish is cooked but top still too light. Serve immediately.