Heat the oven to 250°F and line a baking sheet with parchment paper. In a small bowl, whisk together 4 Tbsp of vanilla instant pudding mix with the flour, corn starch, sugar, and salt. With a spatula, stir in the butter until small clumps start to form. Spread the mixture on a parchment lined baking sheet and bake 20 minutes until sandy. Cool. Return the crumbs to a bowl, stir in the other 2 Tbsp vanilla instant pudding mix and pour the white chocolate into the crumbs, mixing until evenly coated. Set aside.