Essex 196 for 7 (Das 69, Khushi 34, Westley 31*) beat Gloucestershire 195 for 7 (Charlesworth 52, Dent 33) by three wickets
"There is a lot of scope for things to go better but I guess I've had worse weeks," Das said. "I am really happy with how the week has gone and hopefully can keep the ball rolling and keep the momentum going.
"It is very pleasing to contribute with Feroze. I have played with him since club cricket at the age of 13 or 14. It is nice to play with those players you grew up with and shows a really strength to our club; players coming through the pathways and into the first team."
Essex and Gloucestershire hadn't bowled a ball at each other at the Cloud County Ground, Chelmsford since 2016, following an incredible run of five consecutive washouts. Essex had also delayed the start of their Blast season due to the Ireland clash.
Former Eagles Grant Roelofson and Chris Dent got Gloucestershire off to a strong start in the powerplay - 61 for 1 - but the former feathering an edge behind saw them stall.
Miles Hammond and Dent fell in the following two overs, with Ollie Price bowled soon after, leaving the visitors on 80 for 4 just past the halfway point. But after an unspectacular start, where he was dropped on 13 and had 20 off his first 13 balls, Charlesworth went into hyperdrive.
He took Matt Critchley for two consecutive sixes on the leg side before tearing into Sam Cook. Two fours through mid-on were followed by two maximums over deep square - one on the back foot, the other flicked off the front - to take him to his half-century.
Next ball, Cook had the last laugh by finding his edge. James Bracey heaved his first ball for six - which made it 47 runs in 12 balls for Gloucestershire - but next ball he picked out long off, with Jack Taylor coming and going in the same Daniel Sams over.
Danny Lamb, who arrived on a short-term loan from Lancashire before the match, crashed a four and a six off the last over to take Gloucestershire to an imposing 195 for 7.
Fast bowler de Lange had Adam Rossington caught at deep midwicket with his third ball but pulled out of his delivery stride before bowling another ball before walking out of proceedings.
Khushi had already pinged de Lange back over his head before repeating the trick twice off Tom Smith's spin. But he fell to a stunning catch at short third as Essex blasted 72 for 2 in the powerplay.
Das showed his classy shot-making against Ireland but proved his outright power for a small man with 11 fours and sixes straight and over midwicket. His maiden T20 fifty came in 27 balls, although he had earned a life when dropped on 38. He may not have even played had Michael Pepper not suffered a knock in a Second XI match.
The Eagles were well ahead of the rate but were pegged back when Critchley slogged to long-on and Das top-edged a slog-sweep.
Walter was bowled by Price, Sams chopped to short fine and Simon Harmer clubbed to long-on, but Westley eased to the conclusion to condemn Gloucestershire to a third defeat in four.