Heat olive oil in a large pot over medium heat until shimmering.
Add onion, carrots, and celery; sauté 5–6 minutes until tender with a slight bite.
Stir in garlic and cook 1 minute until fragrant.
Add ground beef; cook 6–8 minutes, breaking into small pieces, until no pink remains. Drain any excess fat.
Mix in tomato paste; cook 2 minutes, stirring until darkened slightly.
Sprinkle flour over mixture; stir 1 minute to remove raw taste.
Pour in beef broth and Worcestershire sauce; add thyme leaves.
Bring to a gentle boil, then reduce to simmer for 5 minutes to thicken.
Stir in peas and corn; simmer another 3–4 minutes until heated through.
Toppings
Remove from heat. Dollop mashed potatoes on top, spreading gently to cover surface.
Sprinkle cheddar cheese over potatoes; cover and let sit 2–3 minutes until cheese melts and potato edges turn golden.
Season with salt and pepper to taste and serve hot.
Notes
For smoother potatoes, warm mashed potatoes slightly before topping the soup.Leftovers keep well in the fridge for up to 4 days; reheat gently to prevent drying out.