I used acrylic paints because its easier to mix the exact colour you want. But it would be just as easy to do with polish if you had the right colours available.
The pictures show pretty well the layers I put together to create the effect, but heres a little extra explanation just to be even clearer:
1. Start with a white base.
2. Sponge on a layer of an off white colour.
3. Outline roughly with some dark brown.
4. Add black dots in a grid.
5. Add orangey/brown blobs all over.
6. On some of the blobs, add some darker brown.
7. add black to a few of the dark brown parts (you can also add some black round the edges).
8. Add blobs of the colour used in (2) on some of the black/brown blobs (but not on all of them).
9. Add a layer of top coat to give it a smoothed shiny look.
Here are my original nails with the matzah to compare to: