Cream together the butter and sugar in an electric mixer, with hand held electric beaters, or with a wooden spoon, until light and fluffy. Sift the flour and cornstarch into the bowl, add the salt and mix together until smoothly combined. Tip the mixture out onto a lightly floured surface and knead to a soft dough. Roll out the dough between 2 pieces of parchment paper to a thickness of ¼ inch. Prick the dough all over with a fork and cut into triangles or whatever shapes you like using a knife or biscuit cutter.
*for this recipe I cut the dough into circles using a biscuit cutter. Then I cut a smaller circle out of the centre of half of the circles. Use what is on hand to make the cut. I used a cherry pitter. I also could have used an apple corer. Don’t throw away the centre cut-outs as you will use those as “hats” on top of the marmalade (see picture above)