Chop the pistachio kernels until they are finely ground. I used my Pampered Chef mini chopper to chop my pistachios, in batches, but you could also use a food processor.
Put the butter in a pan and heat on a medium heat until it turns a medium brown colour. For me this took around 8 minutes or so.
Mix the ground pistachios, ground almonds, icing sugar, flour and salt in a large bowl.
Add the egg whites, rose water and ground cardamom and mix until combined.
Add the brown butter little by little, mixing well each time, to ensure it is combined well.
Spoon the mixture equally into a mini loaf tin, muffin pan, or friand tin. Makes 10 financiers.
Bake for 12-15 minutes at 180 degrees in a preheated oven. Remove from the oven when they are starting to brown.
Cool for a few minutes in the tin, then remove from the tin and cool fully on a rack.
Decorate by dusting the financiers with icing sugar and sprinkling over the dried rose petals.