- 1 large Vidalia or other sweet onion
- 8 very thin slices firm white bread, crusts discarded
- 1/3 cup mayonnaise
- 1/2 cup finely chopped fresh parsley
- Cut 4 (1/8-inch-thick) slices from widest part of onion, keeping rings intact.
- Spread each slice of bread with about 1 teaspoon mayonnaise and top 4 slices with 1 onion slice each. Top with remaining bread slices, mayonnaise sides down, then trim onion flush with bread. Quarter sandwiches into small square or triangular sandwiches.
- Arrange 2 sheets of wax paper on a work surface. Spread remaining 2 1/2 tablespoons mayonnaise in a thin layer on 1 sheet and spread parsley evenly on the other.
- Dip all edges of 1 sandwich in mayonnaise to coat, then dip in parsley. Transfer to a tray and repeat with remaining sandwiches.