A career-best 243 from Jaik Mickleburgh and a first Championship century for Ben Foakes enabled Essex to take a firm grip on their Division Two clash against Leicestershire at Chelmsford.
Mickleburgh's effort plus the 120 from Foakes saw their side to 521 and a first innings lead of 156.
By the close, the visitors had slumped to 47-3 in their second innings and were still facing an uphill struggle to avoid defeat.
Resuming on 261-4, Mickleburgh and Foakes negotiated the morning session and a large slice of the afternoon without alarm in taking the score to 421 with a partnership of 270 in 74 overs.
They were finally separated by left-arm spinner James Sykes when he tempted Foakes to drive into the hands of Ollie Freckingham at long-off.
Foakes laced his innings with three sixes and 15 fours in a 198-ball stay before Mickleburgh's marathon occupation of the crease was ended when he was seventh out having been bowled by Freckingham.
Graham Napier weighed in with a brisk 41 before he was caught on the deep square leg boundary attacking Sykes who, on his Championship debut, toiled away for 43 overs while claiming 4-176.
However, it was pace man Freckingham who was the pick of the Leicestershire bowlers as he finished with 3-60 from 27.1 overs.
For most of the day, the visiting captain Matt Boyce could only watch his side being put to the sword from the pavilion, while Greg Smith took over, because he was suffering from back spasms.
And he must have been suffering again when his side embarked on their second innings, Smith departing with only a single on the board when he was caught behind by James Foster off Tymal Mills.
The introduction of Essex off-spinner Greg Smith gained immediate reward when the bowler trapped first innings centurion Ned Eckersley lbw with his first delivery with the total on 31.
Worse was to follow, Smith striking again in his second over by having Niall O'Brien caught behind but the visitors steered clear of further disasters before the close.
The visitors will resume on the final day requiring a further 109 runs to avoid an innings defeat.