Heat a 12-inch nonstick skillet over high heat. Add chicken. Cook, stirring occasionally, until golden brown, about 2 minutes; transfer to a bowl.
Add 2 teaspoons oil and the potatoes to skillet. Cook, stirring occasionally, until golden brown, about 4 minutes; transfer to a small bowl.
Add remaining teaspoon oil, the corn, 2 tablespoons scallion, and the jalapeno to skillet, and cook, stirring occasionally, until corn turns dark brown in spots, about 2 minutes (some kernels may pop). Add tomatoes, and cook until skins just begin to soften, about 1 minute. Add stock, salt, pepper, and reserved chicken; bring to a boil. Fold in reserved potatoes, and sprinkle with marjoram and remaining 2 tablespoons scallion.