1 (1 ounce) package dry yellow mustard
2 tablespoons butter
2 tablespoons finely chopped onion
2 tablespoons coarse salt
1 cup relish
4 ounces Swiss cheese
In a large bowl, mix mustard, butter, onion and salt. Cover and refrigerate approximately 1 hour before serving.
Slice Swiss cheese into 1-inch slices and serve on a bun or plate.