In a large bowl, combine egg, 1/4 cup onion, bread crumbs, 3 teaspoons bouillon and 1 teaspoon chili powder; crumble beef over mixture and mix lightly but thoroughly. Shape into twelve 1-1/2-in. meatballs. Roll in flour.
Heat oil in a 12-in. cast-iron or other ovenproof skillet; brown meatballs. Drain on paper towels. Wipe skillet clean with paper towels. Add tomatoes, garlic, cumin and the remaining onion, bouillon and chili powder to skillet; stir to combine. Add meatballs. Cover and cook over low heat about 20 minutes. Stir in beans.
Combine dumpling ingredients. Drop by spoonfuls onto chili; cook on low, uncovered, for 10 minutes. Cover and cook until a toothpick inserted in dumpling comes out clean, 10-12 minutes longer. If desired, sprinkle with minced chives.