In a large pot, gently heat a little olive oil and sauté the leek, celery, and garlic for 5 minutes until softened.
Add the broccoli, courgette, and rosemary, and cook for 3-4 minutes.
Dissolve the stock cube in the 350ml water and add it to the pot along with the mustard. Bring the mixture to a gentle simmer.
Once simmering, add the milk, ensuring the heat remains low and doesn't boil to prevent splitting. If it does split, don't worry. It will be fine once blended.
Cook for 10-12 minutes until the vegetables are tender. Add the spinach and stir until wilted.
Remove from heat, add the cheddar, ricotta, and blend the soup until smooth. Season with salt and pepper to taste and serve.
Top with crispy pancetta if you wish!
