It depends how far you want to go. It it easy to do it with the spindle mounted on an A/C axis since this enables you to tilt the cutter to the required angle then cut round the edge. It would probably be the quickest way to do it...if you had lots to make.

Buying a V shaped cutter is much easier and should cut quickly. It shouldn't cost more than a few £. I've not really looked at cut 2D but I'd be surprised if you can't do this with it. It it after all only a matter of moving the cutter round on a path offset from the outer edge and at the right depth - both of which are easy to work out if the program will not do it for you.

Alternatively you could use a ball nose cutter, and do lots of passes. That would get a reasonable chamfer, though of course it depends on the stepover used. That's what I'd do if it was a one off (since it will take a long time to cut) and I didn't have the right cutter to hand...or I needed a special angle. (In the not too distant future I intend to do this sort of thing with 5 axis as above...)