Step 1: Prepare Your Veggies. Peel and chop all your vegetables: dice the onions, celery, carrots, and potatoes into 1/2-inch to 3/4-inch pieces. Mince the garlic. It's essential to have everything ready before you start cooking, as this makes the process much smoother.
Step 2: Build the Flavor Base. In a large, heavy-bottomed pot or Dutch oven, heat the olive oil over medium heat. Add the diced onions, celery, and carrots. Sauté for about 8-10 minutes, stirring occasionally, until the onions are softened and translucent, and the carrots begin to tenderize slightly. Add the minced garlic and cook for another minute until fragrant, being careful not to burn it.
Step 3: Introduce the Herbs and Spices. Stir in the dried thyme, bay leaf, salt, and black pepper. Cook for about 1 minute, allowing the spices to toast slightly and release their aromas.
Step 4: Add Liquids and Remaining Veggies. Pour in the vegetable broth and diced tomatoes (undrained). Bring the mixture to a gentle simmer. Add the chopped potatoes and parsnips to the pot. Stir well to combine all ingredients.
Step 5: Simmer to Perfection. Reduce the heat to low, cover the pot, and let your Hearty Winter Vegetable Soup simmer for 25-30 minutes, or until all the vegetables are tender when pierced with a fork. Stir occasionally to prevent sticking and ensure even cooking.
Step 6: The Finishing Touches. Remove the bay leaf from the pot. Stir in the fresh parsley and spinach (if using) and cook for another 2-3 minutes until the spinach has wilted. Taste and adjust seasonings as needed. Ladle your glorious Hearty Winter Vegetable Soup into bowls and serve hot!