Whisk flour cornstarch baking soda and salt in a bowl and set aside.
Beat butter brown sugar and granulated sugar until light and fluffy. Scrape the bowl.
Beat in the egg the yolk and the vanilla until smooth.
Add dry ingredients and mix on low just until a soft dough forms.
Fold in white chocolate chips and most of the freeze dried raspberries. Chill the bowl 30 minutes.
Heat oven to 350 F. Line two light colored sheets with parchment.
Scoop about 2 tablespoons of dough per cookie. Press a small well in each ball. Spoon a tiny dab of cold jam into the well and pinch the dough closed. Roll gently.
Dip the tops in the remaining crushed raspberries and place on the sheets with space between cookies.
Bake 10 to 12 minutes until the edges set and the centers look soft. Do not overbake.
Cool on the sheet 5 minutes then move to a rack. Press a few extra white chips on the tops if you like.