The 24-year-old ex-Crystal Palace marksman's career looked over after being sidelined for two years with a series of crippling injuries.
But Kabba has proved the doubters wrong as he destroyed a frail Ipswich side with no bite following the departures of Shefki Kuqi and Darren Bent.
United forced a couple of early corners before snatching the lead in the fifth minute with a classy Kabba strike.
Midfielder Alan Quinn, back in the side after being left out in the earlier games, rifled in a shot which cannoned off Richard Naylor and the little striker charged in to slam a ferocious right-foot strike low into the far corner from 20 yards.
Midfielder Nick Montgomery picked out Paul Ifill minutes later with Ipswich still reeling, the ex-Millwall man tried a similar strike to Kabba's but miscued and the ball rolled across the face of the goal.
Ifill went closer on ten minutes taking advantage of a poor clearance but from a tight angle he slammed the ball into the sidenetting.
Neil Shipperley saw his shot blocked on 18 minutes, the ball rolled to Kabba whose fierce shot was saved at the second attempt by the diving Lewis Price.
Ifill sliced open the creaking Ipswich defence drilling in a cross from the right flanks, Shipperley reacted instantly as Price kept out the big front man's shot with his legs.
Ipswich, under relentless pressure, were inches away from snatching an equaliser in the 32nd minute, Kevin Horlock's free-kick evading the United wall and curling a fraction wide of the top corner with keeper Paddy Kenny making a late attempt to keep it out.
Kabba almost snatched a second on 43 minutes, wriggling past his marker and finishing with an explosive shot kept out by Price at the near post. Seconds before the interval full-back Leigh Bromby saw his fierce shot crash against the post from a David Unsworth corner.
Ipswich should have been back on level terms in the 57th minute after Kabba upended Spanish defender Luis Castro Sito but Darren Currie produced a tame penalty scooped up by the diving Kenny.
There was further misery for Ipswich in the 86th minute when Sito was red-carded for his second bookable offence, before Kabba grabbed his second in the last minute running on to a Quinn pass to finish clinically from 15 yards.