Cut pound cake in medium-size slices.
Scoop a ball of ice cream and wrap completely with cake slices, patching where needed with smaller pieces.
Wrap balls tightly with plastic wrap, forming a round shape. Freeze at least 5 hours or overnight.
Heat oil in a deep fryer or heavy pan.
Stir cold sparkling water very slowly into flour; whisk in egg to create batter.
Remove ice cream balls, one at a time, from the freezer. Dust the surface with flour. Dip into batter, coating completely. Quickly lower coated ice cream balls into oil; fry until golden, about 25 seconds. Remove with a slotted spoon.
Serve with a drizzle of chocolate sauce before ice cream melts!