Mix sugar,butter,egg,flavor in a bowl add milk powder, flour and make a soft dough, divide it into two and add the cocoa powder to the half and leave the other half plain.

Scoop the plain dough an deflate it, scoop the dark dough and make a ball, place the ball at the center of plain dough and cover evenly.

Use spoon to make the curve design.

Make another small ball with the dark dough.

Place the ball on the cookie and press.