1. Using a sharp knife, slice grapes in half crosswise. Trim uncut sides of each half just enough to achieve a flat bottom so that grapes do not roll around.

2. Using a small melon baller, gently scoop out flesh and seeds of grape, leaving enough flesh to keep grape stable and firm. Repeat with remaining grapes, and store cut-side down in single layers on damp paper towels, tightly covered, in the refrigerator until ready to use. Grape cups may be made 4 to 6 hours before filling.