Gianluca Scamacca scored his first West Ham goal as the Hammers began their latest European campaign with a 3-1 win over Danish club Viborg.
Italy striker Scamacca, David Moyes' marquee summer signing from Sassuolo, netted a first-half header on his full debut.
Jarrod Bowen added a second after the break and although Viborg pulled one back, Michail Antonio rounded things off with the third.
It gave the Hammers some breathing space ahead of the second leg of this qualifying play-off in Denmark next week as they bid to make the group stages of the Europa Conference League.
West Ham were without Declan Rice and Aaron Cresswell, as well as Moyes, with all banned for various indiscretions in the agonising Europa League semi-final defeat to Eintracht Frankfurt in May.
It had also been a tough build-up for Viborg for what was probably the biggest night in their history after two players, Nigerian winger Ibrahim Said and Gambia forward Alassana Jatta, were denied entry into the country due to visa rules post-Brexit.
Nevertheless, burly striker Jay-Roy Grot was proving a handful up front for the visitors, especially for stand-in Hammers skipper Angelo Ogbonna who was making his first appearance in nine months after a cruciate injury.
But Moyes watched on from the stands as almost £50million worth of his summer acquisitions combined to give West Ham a 24th-minute lead.
Former Burnley winger Cornet worked his way to the byline, cut back inside and lifted over a cross for Scamacca to head home at the far post.
Viborg were providing a sporadic threat and when Cornet gave the ball away Grot was sent through on goal, with Alphonse Areola racing out to save with his legs.
The second goal arrived in the 64th minute when Bowen picked the ball up 30 yards out, surged forward and pinged a low drive into the corner.
But four minutes later Viborg halved the lead through a far-post header from Jakob Bonde.
Areola was forced into a flying save from Nils Mortimer to prevent the Danes from drawing level before Antonio scored the third with tap-in from fellow sub Said Benrahma's pull-back.