Melt the butter in a large saucepan over medium low heat. Add the leeks and cook until soft, about 5 minutes.
Add the cauliflower and chicken broth. Increase heat to medium high and bring the soup to a simmer. Reduce the heat to low, cover and let simmer gently until the cauliflower is tender, about 30 minutes. Add thyme leaves and cook for an additional 10 minutes.
Remove from heat and let cool slightly. Using an immersion blender, puree the soup in the pot. Add the half and half cream and stir to combine. Season well and let the soup gently warm over low heat; do not let it boil. Cook until heated through, about 3 minutes. Ladle into warm bowls and garnish with soppresatta chips and serve with roasted garlic spread on toasted baguette slices.
Soppresatta chips: cut soppresatta into thin slices and bake in a preheated 350F (180C) oven in a single layer for 15 minutes or until crisp.