Update (8 May 2010):
Thanks so much to Rachel who has linked my post - check out all the great tutorials she finds at oneprettything.com
and thanks to Samurai mom, I now know the "real" name of this patchwork pattern: Cathedral Windows!
I call it japanese folded patchwork but I'm not sure of the "real" name moreover I have seen various versions of it on the internet - ( for which btw I would be very glad to find some tutorials)
But for now this is how I was taught by my mother, so it is a special post that I would like to share with you today.
First the base: cut squares that you will fold "a la origami style" - bringing the points of the square to the center like so and press
Then flip the square over and fold it again in the same way
Attach the squares by sewing the sides together like so (using a whip stitch)
what you see on the picture is the back of the patchwork
Then I secure the "points" of each square with some stiches like so
Now comes the fun part: choosing fabric and cutting square shapes that should be about 1-2 mm smaller that the area they cover - see the pic
I fold the outer base fabric on the colored square so that it overlaps it a bit and start sewing from the corner with an invisible stitch, I sew the base fabric together at the corner so as to enclose the square in it - if that makes sense - and repeat with the four sides and you're done !