Find an old 100% wool sweater and wash it in very hot water with a little soap. It will shrink, shrink, shrink and that is good...it's called "Felting" the wool. Dry it in a hot dryer and once it's done, you are ready to begin!
After you are done shrinking your sweater, trace your hand on a piece of paper in a mitten shape. Outline the shape with a dotted line as this will be your seam allowance. Cut out the shape and it will be both the left and right hand pattern...just flip it over.
Pin the pattern onto the sweater. Make sure to leave enough room for the other hand. Then just flip the hand to the other side of the sweater for your right hand mitten.
I have used the bottom of the sweater as a cuff - you can make this extra long if you want to fold it over to make a cuff.
Cut the pattern out of the front and the back pieces of the sweater. Depending upon how thick the wool is, you may need some very sharp scissors.
Cut out both hands, reverse the material and sew the mitten together. You can use a machine, or you can sew them together by hand...just do not forget to leave the bottom open for proper hand insertion.
I sewed mine by hand as the two wool pieces were too thick for my machine.
Don't get side tracked...
After you are done sewing the sides, top and thumb, turn both mittens right side out and add some embellishments (if you desire...).
Enjoy your extremely warm mittens!
PS - I knew a woman who was wearing her hand made mittens snow shoveling, and because her hands perspired a lot while doing this activity, the wool shrunk even more and she actually had to cut the mittens off of her hands because they had gotten too small to remove!