Put mushrooms into blender, cover with boiling water and let steep for 5 min
Add tomatoes, one chill, 2 cloves garlic, some basil, salt and pepper and blend until smooth
Heat olive oil in frypan over medium high heat, fry remaining garlic, chilli and prosciutto until garlic is golden brown
Add tomato puree to frypan and simmer over medium heat for around 45 minutes until most of the water has evaporated and sauce has thickened.
Add sugar, salt and pepper to taste.
Serve with fresh basil leaves