Mackems Win Reserve Derby!
The Mackems go back to the top of the Premier Reserve League (North) - a point clear of Manchester City with two games in hand.
Sunderland goalkeeper Darren Ward produced two superb second-half saves to keep Boro at bay and he saved a penalty kick but was unable to prevent Richard Smallwood netting the rebound.
Sunderland took an early lead, Cook stole in at the far post to nod confidently back across keeper David Knight and into the far corner.
Sunderland right-back Michael Kay shoved striker Nathan Porritt in the penalty area. Richard Smallwood took the resulting penalty and, although Ward saved the initial effort, diving smartly to his right, Smallwood followed up well to head home the rebound with the keeper still on the turf.
Boro re-emerged a tighter and better organised unit and the second half was much more evenly balanced.
It was looking increasingly likely that Boro would earn a hard-fought draw when Sunderland struck twice in barely a minute.
Sunderland went ahead in the 82nd minute when Cook, from Easington Lane, grabbed his second of the night.
Boro pressed straight away, looking for another equaliser, but they quickly conceded again, this time Cook turning provider, heading forward to Waghorn from the right of the box and the South Shield-born striker volleying the dropping ball across Knight from eight yards out.
SUNDERLAND RESERVES: Ward, Kay, McArdle (Madden 46), Hartley, Brown, Cook, Weir, Chandler, Luscombe, Prica (Stokes 46), Waghorn. Subs not used: Misiewicz, Fletcher, Reed.
MIDDLESBROUGH RESERVEs: Knight, Oliver,Robinson, Corker, Bennett, Gal-Andrezly (Ottie 79), Saiko, Smallwood, Cronesberry, Porritt, Franks. Subs not used: Gray, Filler, Martin, Shead.
Ref: Paul Curry. Att: 906.