In a large saute pan, melt the butter on medium-high heat. Then add the walnuts, white granulated sugar, and brown sugar. Mix until all the sugar has coated the walnuts. Continue cooking and stirring for 5 minutes on medium-high heat until all sugar has dissolved on walnuts.

Remove the candied walnuts off the heat and pour the candied walnuts on a sheet of parchment paper. Spread the candied walnuts out and allow to cool and harden for at least 10 minutes. Store candied walnuts in a sealed container for up to one week.