Peacock feathers are really fun and can make any cake look unique. They are quite simple to make and can be made in a variety of shapes and sizes.
This is what I used:
any size petal cutter
dusts (I used gold, dark green, teal and purple)
Roll out your white gum paste to approximately 1/8 of an inch thick. Using any size or shape of petal or leaf cutter, cut the gumpaste. Make sure the cut is clean and neat without any rough edges. *NOTE: You can purchase actual peacock feather cutters, however you can use any leaf of petal cutter. You will see in the next step how you can customize the shape.
Because you cut your petal out a little thick you are now able to manipulate the petal by using your rolling pin to widen the petal. Use your rolling pin on top of the original cut, press firmly and stretch out the petal (be careful not to tare the gumpaste). You can see here that I actually made the petal much wider. *NOTE: do not worry too much is the petal gets out of shape.
Now that you have the feather the shape you want you can begin to use the dresden tool. Place the dresden tool about a quarter of the way away from the edge. Press firmly and pull towards the outer part of the feather. Continue to do this all the way around the feather. If your gumpaste tares a bit, do not worry, feathers are not perfect and in fact that have cut edges.
Once you have gone all the way around the feather with the dresden tool, you will have to allow the feather to dry for at least 1-2 hours (or overnight if you have the time). Feathers do not have flat edges so I placed my feather on some contoured foam (or you can use some paper towel) to ruffle the edges slightly.
Now that the feather is dry you can begin to dust or paint. If you wish to have a darker shinny surface you can mix your dust with some lemon extract to create a paint. If you wish to have your feather have a matte look just use dust. For my feather I used gold, dark green, teal and purple.