Herbed Tomato Soup

Bahan-bahan (8 porsi)

• ½ cup (1 stick) butter, (divided)
• 2 tablespoons extra virgin olive oil
• 1 large onion, (thinly sliced)
• 4 sprigs fresh thyme
• 4 large basil leaves, (chopped)
• salt and freshly ground black pepper, (to taste)
• 2½ pounds fresh tomatoes, (peeled and cored)
• 3 tablespoons tomato paste
• ⅓ cup all purpose flour
• 4 cups chicken or vegetable broth
• 1 teaspoon granulated white sugar
• 1 cup heavy whipping cream
• croutons, (for garnish (optional))