Yarn, you're probably thinking, "let me guess!" and you would be right.... Cascade's Magnum (less than one skein; color 9431 was used here). I do use other yarns, I'm just in love with this one!
#15 circulars at least 32"
a crochet hook & darning needle for finishing
1 large button
Gauge: 2sts & 2.75 rows = 1"
This was knit with an adult in mind. As you can see it's a little large on my model here. The neck opening measures @17" from end to end (not including the buttonhole loop). Consider this the frame work for any sort of modifications like casting on fewer stitches for a smaller size; casting on the same amount but with more decreases again for a smaller size; using a lace pattern; adding short rows to create fullness in the back etc.
Cast on 270 sts and work in Stockinette St for 8 rows.
Row 9: k7, k4tog, k1, *k5tog, k1* end with k4tog
Row 10: purl
Row 11: k 6, *k2tog*
Row 12: bind off using the purl st to last 5 sts. Cut yarn leaving a long enough tail to feed through the last 5sts. With a darning needle come back between 2nd & 3rd st (back to front) and with a crochet hook, chain enough sts to form a button hole loop. Slip stitch the loop together. Weave in ends and enjoy!
And if you get a chance, check out this video on hyperbolic crochet.... to continue the theme.