I had to experiment a bit until I was satisfied with a small heart for Mo's arms. I first accomplished a "too large" version, and later adjusted it until I had a small enough, cute heart for Mo. Then I crocheted a second small heart and sewed them together and stuffed it a little bit. I recommend sewing the hearts together with the beautiful side facing out, they are too small to turn inside out (see pictures) - or I'm too clumsy for it to work.
"big" heart: 4.5 x 4.5 cm
Start: magic ring
Rd 1: 7 single crochets in the magic ring and connect with a slip stitch
Rd 2: 2 chain stitches (do not turn!)
5 double crochets in the first stitch,
then 2 half double crochets in one stitch each,
in the next (fourth) stitch: a half double crochet, a double crochet, and a half double crochet,
then 2 half double crochets in one stitch each,
in the last (seventh) stitch: 5 double crochets,
2 chain stitches and connect with a slip stitch in the stitch from Round 1.
For a smaller heart with fewer "holes", skip Round 1 and directly crochet Round 2 in the magic ring - the shape will be retained when the magic ring is tightened.
"little" heart: 3 x 3 cm
Start: magic ring
Rd 1: 1 chain stitch, 1 half double crochets, 3 double crochets, 3 half double crochets, 1 double crochet, 3 half double crochets, 3 double crochets, 1 half double crochets, and to finish of, a slip stich into the magic ring.