Place oven rack on top third of oven. Preheat broiler to high. Halve tomatoes crosswise. Place tomatoes, cut sides down, on a foil-lined baking sheet. Broil 5 minutes or until skins are slightly blackened. Remove and discard skins. Discard foil.
Heat olive oil in a large saucepan over medium-high heat. Add onion; sauté 3 minutes. Add garlic; sauté 1 minute. Stir in tomatoes; cook 2 minutes. Add chicken stock, salt, and pepper; bring to a boil. Stir in cream cheese and basil.
Carefully place tomato mixture in blender. Remove center piece of blender lid (to allow steam to escape); secure blender lid on blender. Place a kitchen towel over lid (to avoid splatters). Blend until smooth. Divide soup evenly among 4 bowls.
Line baking sheet with foil. Coat 1 side of bread slices with cooking spray; turn over. Top 2 slices with cheese and remaining bread slices. Place sandwiches on pan; broil 30 seconds on each side or until toasted. Cut each sandwich into 6 pieces; top servings evenly.