Preheat the oven to 375°.
Cook the amaranth in a very hot skillet, 1 tablespoon at a time, stirring constantly, until it pops, 10 to 15 seconds per tablespoon. Transfer to a shallow bowl and cool slightly.
Add the scallions to the amaranth along with the garlic, mustard, lime juice, salt, pepper and enough oil to make a smooth mixture.