Start by sautéing the onion in a skillet with the olive oil over medium-high heat. You want the onion to become translucent and fragrant, about 3 to 5 minutes.
Next, add the lean ground beef to the skillet. Cook until it’s nicely browned and no longer pink inside. Make sure to drain any excess grease before moving on to the next step.
In your crock pot, combine the sautéed onion and browned beef with the chopped potatoes, carrots, celery, fire-roasted tomatoes, tomato sauce, garlic, and bay leaves. Stir well to combine everything.
Pour in the beef broth and add the Worcestershire sauce, Italian seasoning, onion powder, sea salt, pepper, and red pepper flakes if using. Stir again to make sure all the ingredients are well mixed.
Cover the slow cooker with the lid and set it to low heat. Let it cook for 6 to 8 hours or on high heat for 3 to 5 hours, until the carrots and potatoes are tender.
Approximately 15 to 20 minutes before you’re ready to serve, stir in the frozen corn and frozen peas along with the tomato paste. This will help thicken the broth and enhance the flavor.
Once the soup is done, taste it and adjust the seasoning if necessary. You can add more salt or pepper to your liking.
Serve the soup hot, garnished with a sprinkle of cheese on top if desired. It’s a wonderful way to enjoy a cozy meal!