FOR HAYSTACKS: Melt white chocolate with oil in top of double boiler over simmering water, stirring just until smooth. Mix in 1 cup coconut. Remove haystack mixture from over water.
FOR PIE: Spread half of ice cream in crust. Drop haystack mixture by teaspoons over ice cream. Freeze until haystacks are firm, about 10 minutes. Spread remaining ice cream over. Top with remaining 1 cup coconut. Freeze pie until just firm, about 1 hour. Wrap pie and freeze overnight. (Can be prepared 2 days ahead; keep frozen.) Let pie stand at room temperature 10 minutes. Cut pie into wedges and serve.