In a large pot, warm the olive oil over medium heat. Add the chopped onion and minced garlic, followed by the diced carrot and celery. Sauté these aromatics for about 5 minutes, stirring frequently, until the vegetables are soft and fragrant.
Incorporate the diced potato into the pot and continue to sauté for an additional 3 minutes, allowing it to slightly soften.
Next, pour in the vegetable broth and water, stirring to combine well. Increase the heat to bring the mixture to a gentle boil.
Once boiling, lower the heat to medium-low, then add the frozen mixed vegetables and dried thyme. Stir everything together, allowing the flavors to meld.
Season the soup with salt and pepper according to your taste. Cover the pot and let it simmer for approximately 10-15 minutes, or until the potatoes are tender and easily pierced with a fork.
After simmering, remove the pot from heat and allow it to cool for a few minutes. Using an immersion blender, blend the soup until smooth. If you prefer some texture, you can blend in batches using a standard blender, only blending part of the soup.
Return the blended soup to the pot. If needed, reheat gently on low heat, and taste to adjust seasoning as necessary.
Notes
Ladle the warm soup into serving bowls and garnish with fresh parsley. Pair with crusty bread for a hearty meal.