I believe, quite literally, that you need to create a (solid) star and specify a v-bit. It will do exactly what you want, as long as the depth you specify is deep enough for the v-bit in question. Try it in Easel and look at the detailed preview.
and depending on how deep you want to carve/ how big the star is… you will want to use a different v-bit. … a 60 degree bit will have to be deeper than a 90 degree bit at the same size. and a 90 degree bit will be deeper than a 120 degree bit