Preheat the oven to 350 degrees F. Grease a large baking sheet.
In a mixing bowl, combine the peanut butter, 1 cup sugar replacement, the egg, and vanilla, and stir well with a spoon. Roll the dough into balls the size of walnuts. Place the balls on the prepared baking sheet. With a fork, dipped in sugar replacement to prevent sticking, press a crisscross design on each cookie. Bake for 12 minutes, remove from the oven, and sprinkle the cookies with some of the remaining sugar replacement. Cool slightly before removing from pan.