I know exactly what you mean, Sue, as I have an old magazine with a project including this technique (I have a feeling it was by Jane Gill, but I may be imagining that).

The magazine will require a bit of rooting out, if you bear with me.

I have a feeling that you need to punch out hearts in several sizes and then shape them using a double ended embossing tool before gluing together.

Try googling "floral punch craft" and you might turn up something useful.

Welcome to UKS, by the way.