In a large bowl, with electric mixer on low, then medium speed, beat together the butter, powdered sugar, cornstarch, sugar, salt and vanilla until light and well blended -- about 3 minutes.
Beat or stir in flour until evenly incorporated.
Let the dough stand for 5 minutes, or until firmed up slightly.
Divide the dough in half, place each portion between large sheets of wax paper. roll out each poriton, 1/3" thick, check the underside of the dough and smooth out any wrinkles that form. Stack the rolled portions(paper still attached) on a baking sheet, refrigerate for 30 minutes until chilled and firm -- or freeze for 20 minutes to speed chilling.
preheat oven to 300*.set out several baking sheets. working with one portion of dough at a time, leaving remainder chilled -- gently peel away, then pat one sheet of wax paper back into place.
Flip the dough over, then peel off and discard the second sheet.
Using a 2/3-3" fluted, daisy or round cutter or other size and shape.for your stamp -- cut out the cookies.
If at any point the dough softens too much, transfer the paper and cookies to a sheet and rechill --.
Using a spatual, carefully transfer the cookies to baking sheets, spacing 1 1/2" apart. Reroll any dough scraps. Continue cutting out the cookies until all the dough is used. Bake the cookies, one sheet at a time, upper third of oven for 10 minutes. Remove the cookies from the oven, using a cookie stamp, press a design into the top of each cookie. Return cookies to oven and bake for 15-20 minutes more or just tinged with color all over and fairly darker at the edges. Reverse the sheet from front to back halfway through baking to ensure even browning.transfer cookies to rack and let stand until cookies firm up. about 10 minutes. If desired, the designs stamped into the cookies can be highlighted by painting with a color wash.(see below).
Store in an airtight container for up to 2 weeks or freeze up to 2 months.COLOR WASH*** Prepare a wash by adding a drop or two of desired color to a few teaspoons of water. Make as many different colored washes as desired. using a small clean artist brush, test each color on a broken cookie to get desired color -- lightly apply the wash over very fine details using small brushes.it is best to add only a light wash and keep colors in pastel range. let cookies stand 1-2 hours or completely dry -- .