You won't miss the sugar in these cookies, which I adapted from a traditional recipe. The splenda should be the type that measures the same as sugar. If not, you want enough to equal 1/4 cup sugar. I recmmend using either all butter or at least 1/2 butter and half margarine, I also highly recommend using the St. Dalfour Strawberry Preserves, otherwise you won't get as good results. They are absolutely wonderful, sugar free with no artificial sweeteners and much better and more flavorfful than any other brand I've ever tried. I can't even tell the difference between the St. Dalfour strawberry preserves and those with sugar. It's worth the effort and price if you can find them. The company has a website you can order from, and tther flavors are great as well. Also note that if you plan to store the cookies for a bit, it might be better to bake them without the preserves and fill them just before serving.