Throughly rinse produce and pat dry. Trim and thinly slice green onion. Mince garlic.

Have tomatoes set up (in the next step) at your cooking station to prevent garlic from getting overcooked - adding them quickly will cool the pot down. Heat 1 tsp. olive oil to a medium pot over medium heat. Add garlic to the pan and cook for 30-45 seconds, or until fragrant.

Add canned tomatoes, sugar, basil, vegetable base, and 1 cup of warm water to pot. Bring to a boil, reduce to a simmer, and cook for 8-10 minutes.

While the soup is cooking, heat 2 tsp. olive oil in medium pan over medium heat. Brush one side of sourdough bread slices with truffle oil. Place a piece each of Swiss cheese and cheddar cheese between two slices of bread, truffle oiled-sides in. Add sandwiches to pan and cook for 3-4 minutes on each side, or until golden brown and cheese is melted.

Turn off heat. Slowly stir half of the sour cream into the soup (reserving remaining for garnish.) Season with a pinch of salt and pepper. Gently stirring in sour cream off heat prevents it from separating or "breaking", and makes for a smooth and enriched sauce.

Place equal amounts of tomato soup into two soup bowls. Garnish with a dollop of sour cream and green onions. Cut grilled cheese sandwiches in half and stack three halves per serving next to soup.