In a large mixing bowl, combine the butter and sugar. Beat with an electric mixer for about 1-2 minutes or until pale and fluffy.
Add the cornstarch, flour, crushed Craize, vanilla, and a pinch of salt.
Place the dough onto a piece of saran wrap and form into a long log. Cover and refrigerate for 1-2 hours or until the dough is firm.
Slice into ¼” rounds and place on a lined baking sheet. Bake at 350 degrees Fahrenheit for 12-15 minutes. The cookies will still be soft when coming out of the oven. Let cool completely.
Once cool, place a generous amount of dulce de leche onto the bottom of one cookie, and place another cookie on top to form the “sandwich”. Repeat with the remaining cookies.