Both made their third test centuries as part of a 236-run partnership, New Zealand's overall record for the fifth-wicket. They eclipsed the mark of 222 set by Craig McMillan and Nathan Astle against Zimbabwe at Wellington in 2000. The pair had earlier surpassed the 195 they made to resurrect first test hopes in vain last week at Lord's.
Their effort also became the highest stand for any New Zealand wicket in England, beating Martin Crowe and Bruce Edgar's 210 for the third at Lord's in 1986.
Blundell was eventually dismissed for 106, leaving the visitors at 405 for five, caught by England captain Ben Stokes at mid-off from spinner Jack Leach.
Mitchell reached his century from 184 balls with an edge through a vacant third slip off Matt Potts. The innings marked the sixth test ton by a New Zealander at Trent Bridge and the fourth after Bevan Congdon (1973), Victor Pollard (1973) and Martin Crowe (1994) across successive tests in England.
Potts sneaked through his defence on 98 but the ball hit outside the line. In a blow for the right-armer he then dropped his nemesis on 104 at long on off Leach.
Mitchell remained on 128 at lunch, with debutant Michael Bracewell five.
Blundell accomplished his ton in 191 balls, 11.2 overs after his batting partner, by pushing into the legside for a single off Leach.
The sheer power of Mitchell meshed with the impish elegance of Blundell. Mitchell was the lumberjack with the axe, Blundell was the fencer with the foil. They absorbed pressure with alacrity, confronted their opponents where necessary and regularly rotated the strike.
Mitchell had a penchant for attacking Leach, which included depositing him into local fan Susan's pint of cider in front of the pavilion. The Black Caps dressing room, seizing a goodwill opportunity, ensured a replacement was dispatched.
Blundell used his hand-speed to savage width, particularly anything resembling a half-volley outside off stump.
The partnership reaped benefits where other stands stumbled. That was helped by Root spilling Mitchell on one off Stokes at the end of the 43rd over on 169. A sharp chance from Blundell on 47 off Leach also flew past him on 277.
The Black Caps made the most of the compacted pitch block and appreciable bounce by getting shots to race away square of the wicket.
The top four met expectations but, unlike Mitchell and Blundell, squandered the chance to cash in.
Promise, intent and determination were evident, but undone by concentration lapses. Still, after being 12-4 and 56-4 in the opening fixture, the signs of healing were marked.
A controlled and disciplined opening partnership of 84 between Tom Latham and Will Young built faith but the value of that investment dissolved in consecutive deliveries bridging the 21st and 22nd overs.
Young demonstrated signs of an epiphany after a pair of hesitant singles at Lord's. The right-hander executed a series of slashing cuts, dismissive pulls and flowing drives on his way to 47. Eventually, Stokes had him prodding at a delivery outside off stump, which flew low to second slip Zak Crawley.
Latham was more compact, checking and punching his strokes with efficiency as part of 26.
The stand-in skipper for nine of the last 18 tests in Kane Williamson's absence played a responsible hand to avoid facing a 45-7 oblivion from the first day of the series.
Henry Nicholls with 30 and Devon Conway with 46 also looked assured.
The match also holds significance for Bracewell, who had begun his maiden innings in Williamson's Covid enforced absence. He is New Zealand's 283rd test cricketer and the fourth member of his wider family to achieve the feat after uncles John and Brendon and cousin Doug.
