UPDATE (8/10/09):  I'm leaving this up, but grudgingly.  Knitted objects show up in the fourteenth century, but mostly in Knitting Madonnas, and I haven't seen evidence to support a knitted chaperone yet.  So I'd have to come down on the side of PERIOD-ISH for this guy.  And since I've discovered I'm not into 14thc any more, it's out of persona for me.  But hey, it's an intermediate design, and it works to stay warm, and a kid would probably enjoy it.

(This is my own pattern for a knitted hooded mantle, or chaperon, as seen below, and guessed at from a finished chaperon – which was black, and slightly felted -grumble grumble.  I made some changes, and this is my writeup of what I did.  Use it in good health, but please do not sell your products made from this pattern -trade them! Or come up with your own.  Thanks~Greet)

Yarn: Berroco Ultra Alpaca, color #6285, call it 'Peacock', 215 yards/skein, 100g.  I used 3 skeins to fit me, who's 5'-7" with a shoulder dimension of 17".
Needles: US8 (5mm), 36" long.
Gauge: 4 sts/inch x 5 sts/inch on US8 – but it doesn't really matter, see instructions.
At least four stitch markers
Some sort of double-ended stitch holder that will hold ~20 stitches.

This chaperon is knit from the bottom up, in the round.  You can start with the body of the mantle first, and add the edging later, which is what I did with the example above, or start with the edging first.  If you have any qualms about being able to adapt the repeats of your edging to the hem of your mantle START WITH THE EDGING FIRST.  I like to live dangerously.

EDGING FIRST

Diagonal dagged edge

Cast on four stitches.  *Knit 3 stitches, increase in last stitch by knitting in the front and the back.  Turn.  Knit reverse side (4 sts).  Repeat from*, adding a stitch on every right-side row until twelve stitches on needle.  Knit reverse side (12 sts).  **Knit 10 stitches, K2tog, K1.  Knit reverse side (11 sts).  Repeat from ** until four stitches left on needle.  Knit reverse side (4 sts), one dag completed, 16 rows.

There's some other edgings from my copy of Nicki Epstein's Knitted Embellishments that would be fun to try, a Knight's edge, and a Serf's edge.  I'll let you find them.

Knit selected edging pattern until edging is long enough to go around shoulders.  Graft end to beginning and form a loop.  Pick up stitches on the non-dagged side of your edging – MAKE SURE THE NUMBER OF STITCHES ARE DIVISIBLE BY FOUR.  The example above, at gauge, was 256 stitches.  Cheat, if necessary, by increasing or decreasing on the first row to end up with a multiple of four.

LEAVING EDGING UNTIL LATER
Cast on a number of stitches that is divisible by four, and that will fit around your shoulders at gauge.  The one above is 256 stitches.

Place markers at each quarter mark of your circumference.  Knit stockinette, decreasing at the markers as follows on EVERY OTHER ROW.  3 sts before marker, K2tog, K1.  Pass marker.  K1, SlK2.  Decrease in this fashion until the distance between your markers equals 6".

Decide which quartile of your mantle will be the front.  Move your back quartile markers to frame the center 8 stitches of the 'front' quartile.  Put these stitches on a stitch holder.

(If you screwed up somewhere, and there's a center NINE stitches, that's okay – that's what I did.  If anybody gives you a hard time for having nine stitches under your chin, you have my permission to give them funny looks.)

Now, you're going to stop working in the round, and start working flat, but on all the stitches except the ones on the holder.  Knit one row entire, purl that edge stitch, then stick it on your holder.  Keep purling the rest of the row, get to the end, turn, knit that edge stitch, then stick it on your holder.  Continue this way until you reach your original front quartile markers.

Okay, now knit back and forth on the hood until it's ___" long from the stitch holder in front.  Now it's time to decrease the back seam of the hood, so it forms a round head shape.  YOU DON'T HAVE TO DO THIS – you could just keep going back and forth until the hood is big enough for your head, and then graft the top together, which would give you a square hood shape, and a short point at the back.  (Alternatively, if you're really nuts, you could increase in the middle instead of decreasing, which would make a liripipe.  I have visions of getting yanked around by my liripipe, since I'm one of those people that attracts teasing, so no 'pipes for me.)  In any case, place a marker in the center of the hood stitches that you've got left.

Decrease EVERY OTHER ROW just like you did for the quartiles, until the hood is deep enough for your head.  Graft the two halves together using kitchener, and now we move onto the facehole.

Pick up stitches around the facehole using your circular, Be generous with your pickups – at least 3 pickups for every four rows, since we're going to be ribbing, and ribbing cinches in.  K2P2 rib until happy with the way the hood looks – try on frequently.  Bind off in rib pattern.

IF YOU LEFT THE EDGING UNTIL LAST
it's still not done. I did this, and DON'T RECOMMEND IT, but if you're stuck with it…

Follow the directions above, for the dagged edging, with the following variation:  Cast on four stitches.  This is the reverse side.  Turn.  Orient your chaperone such that the hood is on your right, and you're sticking the empty right hand needle through an open edge stitch, somewhere on the side or back.  Ignore this stitch, and knit the first of your 4 cast-on stitches.  Now, pass the picked-up edge stitch over the first knit stitch, then continue with the rest of the row.  Don't forget to do the increase at the end.  Turn the needles (you don't really have to flip the whole chaperon) and knit back the other side.  Turn back to the right-side, and pick up the next edge loop. 

Continue in this fashion, until you make it all the way around, praying that the stitch count comes out right.  Dance, crow and preen when it does.  Now, cast off those four stitches on your needle, and sew them to the original cast-on four stitches.