2 heads of broccoli (approx 800g), cut into florets
150g Gruyère, grated
3 tbsp double cream
Dry-fry the mustard and fennel seeds over a medium heat until the mustard seeds start to pop. Using a pestle and mortar, grind the seeds to a fine powder.
In a large saucepan, fry the chorizo (without any oil) for 4 mins over a medium heat until it releases its oils, then use a slotted spoon to transfer it to a plate and set aside.
Add the oil to the pan and tip in the onion and garlic. Cook for 10 mins until the onion is softened. Stir in the ground spice mix and fry for a further 1 min, stirring continuously, before adding the broccoli and chicken stock. Bring the liquid to the boil, then put a lid on the pan, turn the heat to low and leave the soup to simmer for 5 mins or until the broccoli is tender.
Blend the soup until completely smooth in a food processor, or with a stick blender, then stir in two-thirds of the Gruyère and the cream. Season to taste. Spoon into bowls and top with the remaining cheese and the chorizo.