Place butter, sugar and walnuts in a frying pan over medium heat.

Once the butter has melted stir the mixture constantly until the sugar and butter mixture is no longer granular and has caramelized. This will take 4 to 5 minutes. 

When the mixture has caramelized stir a few more times to evenly coat the walnuts and then turn out onto a silicone dish or parchment paper to cool. 

When the walnuts have cooled break them apart before serving, or heck leave them in large clumps, it's up to you. They taste great either way!