An inbound NAT entry should do it, no need to use 1:1 if you're only running a single server on your LAN. Be sure to also create a firewall rule on the WAN, which you can do automatically when creating a NAT mapping.
As for DNS, just setup your DNS entry so that blackserver.white.com points to mono's WAN IP address. Mono also supports dynamic DNS, see the "Dynamic DNS" page in the "Sevices" menu of your mono's GUI.
Handbook entry on NAT:
http://doc.m0n0.ch/handbook/nat.htmldb