Butter each slice of bread and sprinkle with Parmigiano, pressing to help it adhere. Invert the slices onto a work surface, cheese side down. Top 4 of the slices with the Swiss cheese, ham and pickles. Mix the mustard and preserves and spread on the remaining 4 slices of bread. Close the sandwiches and griddle over moderate heat, turning, until golden, crisp on the outside and melted inside, about 3 minutes. Cut in half and serve right away.