If you'd like to use a filling such as a jam, jelly, pudding, curd or anything that you can think of, it should be placed in a piping bag with a special doughnut filling tip or plain round tip. Find a spot on an edge of a doughnut, insert the tip, and squeeze the filling into the doughnut. When you feel the doughnut become heavy and the filling starts to come out, you know that doughnut is filled to the max. Enjoy!