Vesperlark | Body Double | Yahenni, Undying Partisan

Cards

Vesperlark in your graveyard.
Body Double and
Yahenni on the battlefield (
Body Double as a copy of
Vesperlark).

Activate
Yahenni, Undying Partisan by sacrificing
Body Double.
When
Body Double leaves the battlefield, its
Vesperlark ability triggers, returning itself from your graveyard to the battlefield as a copy of
Vesperlark.
Resolve the
Yahenni, Undying Partisan ability.
Repeat.