1. Apply your base polish.
2. Draw the body by painting a circle.
3. Draw two parallel lines over and under the body.
Bend the top one up a little at the corners.
4. Paint the rest of the hat and make the top a bit pointy.
Draw the end of the broom.
5. Paint the hair and do the little feet.
6. Draw the eyes with a white polish. Let dry.
7. Draw the rest of the eyes and a long pointy witch nose.
Do some effect drawing on the broom if you want to.
8. Seal the manicure with a top coat. Done!
I used H&M's Peach Me Soon as base and then did the drawing with Barry M's Nail Art Pens. You can of course use any black, silver and white polish you like with a thin brush and dotting tools instead.
Good luck! Don't hesitate to ask me if you have any questions!