Heat a nonreactive pot or enameled dutch oven over medium heat.
Add butter then add chopped onions. Sauté 10-12 minutes, stirring occasionally, until softened and golden.
Add minced garlic and sauté 1 minute until fragrant.
Add crushed tomatoes with their juice, chicken stock, chopped basil, sugar (or add sugar to taste), and black pepper. Stir together and bring to a boil then reduce heat, partially cover with lid and simmer for 10 minutes.
Blend with an immersion blender.
Add 1/2 cup heavy cream, 1/3 cup freshly grated parmesan cheese and return to a simmer. Season to taste with salt and pepper if needed and turn off the heat.*
Ladle into warm bowls and top with more parmesan and chopped fresh basil.