1. Preheat your oven to 200°C (400°F).

2. Thoroughly wash and peel the parsnips and potatoes. Cut them into small, uniform pieces to ensure even cooking.

3. Arrange the chopped vegetables on a parchment-lined baking sheet. Drizzle with oil and season with salt to taste.

4. Roast the vegetables in the preheated oven for approximately 25 minutes or until they are tender and lightly golden.

5. Carefully transfer the roasted parsnips and potatoes to a large pot. Add 500 milliliters (2 cups) of water, 100 milliliters (7 tablespoons) of the vegetable stock concentrate, and 200 milliliters (scant 1 cup) of the heavy cream to the pot.

6. Using an immersion blender, blend the mixture until smooth and creamy. If necessary, add more water to achieve the desired consistency.

7. Taste the soup and season with additional salt and freshly ground black pepper as needed.

8. In a separate skillet, fry the bacon over medium-high heat until crispy. Remove the bacon from the skillet and drain on paper towels.

9. Slice the mushrooms thinly and sauté them in the leftover bacon fat until they are golden brown and tender.

10. Ladle the hot soup into bowls or cups. Top each serving with the crispy bacon pieces and sautéed mushrooms.

11. Garnish each bowl with a sprinkle of fresh thyme leaves. Serve immediately and enjoy!