In a bowl, sift together the flour, cornstarch, salt and baking powder and set aside.
In a larger bowl, cream the shortening, margarine and sugar with electric beaters until the mixture gets all soft and fluffy, for at least 4 minutes.
Scrape the sides of the bowl with a rubber spatula to ensure everything mixes in. Now beat in the vanilla and lemon extracts and the soymilk until everything is just combined.
Beat in half the flour and when it is thoroughly moistened, and then mix in the rest to form a soft dough.
Divide the dough into two and pat each portion into a disc. Wrap each disc in plastic wrap and refrigerate for a few hours or overnight.
On a lightly floured platform or board, roll each disc to about 3/8ths-inch thickness. Cut it into shapes with a cookie cutter. Place the cookies on a baking sheet lined with parchment paper, about 1-inch apart. Reroll leftover scraps and shape into more cookies.
In a preheated, 350-degree oven, bake the cookies for about 10 minutes until done.
Remove the cookies from the oven and allow them to cool for five minutes. Then transfer to a wire rack to cool completely before decorating.
(Recipe from the book Vegan Cookies Invade Your Cookie Jar by Isa Chandra Moskowitz and Terry Hope Romero, published by Da Capo Lifelong, a member of the Perseus Books Group. Copyright © 2009. www.dacapopresscookbooks.com)