Heat a drizzle of oil in a large skillet over high heat. Season chicken well with salt and pepper, and brown well. Remove, pour off fat.
Halve and pit the plums, and place them cut-side down in the skillet. Brown well, remove and reserve.
Add remaining tablespoon oil to the pan and sauté ginger and garlic a minute or 2. Add teriyaki sauce, stock and whisk in plum preserves and poppy seeds. Simmer to thicken and combine. Once the sauce coats a spoon, add chicken back and turn in sauce to coat. Cover and simmer to cook through.
Serve Poppy-Teriyaki Chicken with plum halves and rice topped with lots of scallions alongside.