Cut luncheon meat into 8 slices; brush each slice with syrup, reserving remaining syrup.
Arrange meat slices around edge of a 9-inch pie plate.
In saucepan combine beans, remaining syrup, onion, flour, and mustard.
Cook and stir till thickened and bubbly; pour boiling bean mixture into pie plate.
Sprinkle with cheese.
Bake at 350° till meat is lightly browned, about 20 minutes.