In large skillet melt butter and olive oil.
Add onions and garlic. Cook over medium heat until onions are golden brown (about 10-12 minutes).
Add tomato paste, thyme and basil, cook for additional 2-3 minutes.
Stir in tomatoes with juices, sugar, pepper, chicken broth and pepper.
Season with salt as needed. Saltiness of broth and tomatoes vary, so salt to taste.
Reduce heat to low, cover and simmer for 30 minutes to allow flavors to meld.
Using an immersion blender puree soup. (any blender will work). If you like a really smooth soup, strain through a sieve.
Stir in mascarpone cheese. Simmer for an additional 10 minutes
Serve warm with a Mozzarella Grilled Cheese Sandwich using top quality Tre Stelle mozzarella cheese.