Preheat your oven to 180 C or 350 F. Line a 8 inch square pan with foil or parchment paper such that atleast two opposite sides are long enough ( to pull out the blondies when done). In a double boiler or a thick bottomed saucepan, take the butter and white chocolate (both chopped to small pieces) , heat on low . Stir continuously or often until both are melted and mixed smoothly.
Take off heat and whisk in the sugar
Whisk in the eggs , ONE BY ONE . Whisk well after each egg.
Whisk in the vanilla
Add the flour and salt. Whisk until combined (you cant see flour anymore )
Add the candied fruit or tutti frutti , reserve a hand full. Fold in gently.
Pour the thick batter into the prepared pan immediately and smooth the top. Sprinkle reserved fruit on top
Bake at 180 C / 350 F for 20-22 minutes until a toothpick inserted comes out with moist crumbs. The edges would have separated from the sides of the pan and may be light brown (but dont wait for this , decide doneness based on toothpick test)
Cool in pan, lift out blondie slab and slice !