In microwave, melt butter, choc chips and dark chocolate, in 30 secs intervals
Beat egg white, sugar and vanilla essence with your balloon whisk til somewhat foamy
Mix dry ingredients in a bowl
Pour melted choc into egg white, fold
Add in dry ingredients, mix til just combine
Add in chopped pecans and walnuts, followed with marshmallows, fold just to coat (do not overmix)
Pour into parchment lined pan
Top with pecans and walnuts, bake at preheated 350 F