To make the soup: In a large stockpot, heat the olive oil over medium heat. Add the onion and sauté until translucent, 3 to 5 minutes. Add the garlic, and sauté for about 1 minute.
Add the tomatoes, stock, tomato paste, and nutmeg. Bring to a boil, reduce the heat, and allow it to simmer uncovered until the flavors meld together, 30 to 40 minutes.
Working in batches, place the soup into a blender, and puree. Pour the pureed soup back into the stockpot, and add the milk. Bring it to a simmer over low heat. Season with salt and pepper to taste. Pour into 6 decorative teacups, and serve. If made ahead, reheat in a large pot over medium heat, stirring for 5 minutes, or until hot.
To make the sandwiches: Place 2 slices of cheese between 2 slices of wheat bread. In a large skillet or on a stove-top grill, melt 2 to 3 tablespoons of butter, then place 2 to 3 sandwiches in the skillet (making sure that they are sitting flat and are not crowded).
Press the sandwiches down with a spatula. When the sandwiches are golden on the bottom, flip onto the other side. Add 2 to 3 tablespoons more butter, making sure to keep the surface well greased. When golden on both sides, transfer to a cutting surface. Repeat to make the remaining sandwiches.
Press a large snowman or other cookie cutter into the center of each sandwich. Remove the remnants. Place your ornamental sandwiches on a plate, and serve with the tomato soup.