Bite-size peanut butter cups are gently pressed on each sugar cookie, providing the basket for these festive May Day cookies.
Beat butter with an electric mixer on medium to high speed for 30 seconds. Add the 1/2 cup sugar, vanilla, and 1/4 teaspoon salt; beat until combined, scraping sides of bowl occasionally. Beat in egg yolk. Beat in as much of the flour as you can with the mixer. Stir in remaining flour with a wooden spoon.
Shape dough into 1-inch balls. Roll balls in the 1/4 cup sugar; place 2 inches apart on an ungreased cookie sheet. Flatten until about 1/4 inch thick. Bake in a 350 degree F oven for 8 to 10 minutes or until bottoms are lightly browned. Remove from oven. Transfer to wire racks and cool for 2 minutes. Press a peanut butter cup half, cut side down, into each cookie; cool completely.
To decorate, tint portions of frosting desired colors with food coloring. Pipe a basket handle, flowers, and leaves above candy basket as desired. Makes about 48 cookies.