Melt the butter and soon it will start foaming up.
Watch carefully and stir occationaly.
After about 5 minutes, it will start browning.
You will see brown bits on the bottom of the pan and smell nutty aroma.
Remove from the heat and pour into a heat proof bowl, leave it to cool.
Put it in the fridge until solid.
Beat the solid brown butter. Add the soften cream cheese.
Beat in icing sugar and vanilla until smooth.
If you wish to make it softer frosting, add a little bit of cream. Or if you wish to make it thicker, add icing sugar.