I used a #3 crochet hook.. Made woth #10 Crochet coton The embroidery thread version uses 3 to 4 skeins of floss. There are detailed instructions, and pictures of almost every step.
To make the heart pin, I used metallic embroidery thread. To stiffen the edges I crochet over a short length of nylon fishing wire. I gave it a sharp crease at the cleavage of the heart. Another idea would be to crochet the last edging over thin wire.