Combine chicken stock and cornstarch in a small bowl, stirring with a whisk.
Heat oil in a large saute pan over medium-high. Add beef and cook for 5 minutes, stirring to crumble.
Stir in Worcestershire sauce, 1/2 teaspoon pepper, 1/2 teaspoon salt, garlic powder, onion powder, and white parts of green onions. Cook for 2 minutes.
Remove mixture from pan using a slotted spoon (you want to keep some of the drippings still in the saute pan). Add the pearl onions to pan and cook 2 minutes.
Add the tomatoes and ketchup, and cook for 3 minutes.
Stir in cornstarch mixture, remaining 1/2 teaspoon pepper, and remaining 1/4 teaspoon salt. Cook 3 minutes or until thickened.
Stir in beef mixture and green parts of green onions. Sprinkle with chives.
Serve over polenta.
Notes
If you make this recipe, share a photo on Instagram and tag me @icancookthat!