Sew buttons on ice cream

What is the origin and meaning of "sew buttons on ice cream"? A relative of my husband would always reply to "So?" with Sew buttons on ice cream"

sounds American to me,the OED has ice-cream first used in 1744 if that is any help.

sorry,as to meaning,I think your relative is wrong,the phrase more naturally is "It is like sewing buttons on ice-cream"-meaning an utterly futile task.