In a physical and scrappy game Munster found their way through the Ulster defence on four occasions, twice in the first half and twice in the second.
The first try coming off an Ulster error after centre Michael Allen's try-line clearance found Jeremy Manning chasing down the sideline to dive over for Munster's opening score . Cusack missing the convert.
Ulster were awarded with a penalty after 16 minutes with James McKinney giving his side three points.
After a great break from winger Ronan O'Mahony up the centre Munster started building the phases making their way inside the Ulster 22. Scrumhalf Duncan Williams spotted a gap and went himself to score Munster's second try.
Cusack added a penalty just before the break giving Munster a 13-3 lead at halftime.
Dave Ryan made way for Dave Kilcoyne for the final 40 as Munster continued to battle on and were rewarded with a second Jeremy Manning try after 48 minutes. The kiwi, returning from injury, certainly made his presence felt today enjoying his time in the centre, aggressively attacking the line and proving solid in defence.
Stephen Archer added the final try on the 61st minute, coming after a series of drives from the pack, with Cusack adding the final score of the afternoon giving Munster a 27-3 win over Ulster Ravens.
Manager Mick Galwey after the win "It was a great display out there today from the young lads as they proved their hunger and dedication once again and they have now secured a place in the B&I Cup Final."
"The work they have done throughout the season is paying off and today's performance is down to everyone involved, from the 22 playing today across the board to the 40 or so we work with, it has been great!"
Munster: Mossy Lawler (Shannon); Ronan O'Mahony (Garryowen), Danny Barnes (Dolphin), Jeremy Manning (Cork Con), Sean Scanlon (UCC); Declan Cusack (Thomond), Duncan Williams (Cork Con); Dave Ryan (Dolphin), Mike Sherry (Garryowen), Stephen Archer (Cork Con); Dave Foley (UL Bohs), Ian Nagle (Cork Con); Tommy O'Donnell (UL Bohs), Eoghan Grace (Shannon), Peter O'Mahony (Cork Con) capt. Replacements: Sean Henry (UL Bohs) for Mike Sherry (75), Dave Kilcoyne (UL Bohs) for Dave Ryan (40), Dave O'Callaghan (UCC) for Tommy O'Donnell (68), Paddy Butler (Shannon) for Eoghan Grace (58), Conor Murray (Garryowen) for Duncan Williams (65), Mike Kelliher (Richmond) for Danny Barnes (65), Luke O'Dea (Shannon) for Mossy Lawler (73).
Ulster Ravens: David McIlwhaine (Queens University), Tommy Seymour (Ballymena); Michael Allen (Belfast Harlequins), Johnny Shiels (Queens University), Chris Cochrane (Dungannon), James McKinney (Queens University), Ian Porter (Queens University); Paddy McAllister (Ballynahinch), Nigel Brady (Dungannon) capt, Declan Fitzpatrick (Dungannon); Andrew Linton (Queens University), Neil McComb (Belfast Harlequins); Ali Birch (Dungannon), Stephen Dougall (Malone), Scott Lavella (Trinity College). Replacements: Niall Annett (Belfast Harlequins), Paul Karayiannis (Queens University), Niall Magee (Dungannon), Stuart McKenzie (Dungannon), Michael Pyper (Queens University), Luke Marshall (Ballymena), Craig Gilroy (Dungannon).