1. Combine 30g (1 oz) of flour and 10g (0.35 oz) of vegetable broth powder in a small bowl.

2. In a large pot, add 1L (4 cups) of water and bring to the boil over high heat (around 212°F/100°C).

3. Gradually whisk in the flour mixture to thicken the soup.

4. Add 250g (9 oz) of frozen summer vegetables, 1 teaspoon of salt, and 0.5 teaspoons of pepper to the pot.

5. Cook over medium heat (around 180°F/82°C) until the vegetables are thawed and tender.

6. Stir in 20g (0.7 oz) of chopped parsley and cook for an additional minute.

7. In a separate bowl, whisk together 250ml (1 cup) of milk and 125ml (0.5 cups) of heavy cream.

8. Gradually add the milk mixture to the pot, whisking constantly to prevent lumps.

9. Bring the mixture to a simmer over low heat (around 145°F/63°C) and cook until heated through.

10. Stir in 50g (1.8 oz) of baby spinach and cook until wilted.

11. Serve hot, straight from the pot.