Preheat oven to 200C/390F.Place the broccoli, onion and garlic into a lined roasting tray.Sprinkle over the oil and salt.Roast in the oven for 20 minutes, remove and stir.
Return to the oven for another 10 minutes, until lightly browned.Place the butter and thyme into a saucepan over medium heat and saute until the thyme becomes fragrant.Add the roasted broccoli, onions and garlic and stir well.Add the heavy cream and stock and bring to a simmer.
Simmer for 10-15 minutes, until the broccoli is tender.Remove from the heat and blend the soup using a stick blender.
Once smooth, add the cheddar and pepper and blend again.
If the soup is too thick, add a little hot water.Taste and add more salt if desired.Serve and enjoy.