The strike duo shared all five goals between them in the Lions' demolition of Dagenham & Redbridge in an FA Cup third round replay at The Den on Tuesday night.
Henderson netted his second hat-trick of the season whilst Spurs loanee Harry Kane bagged a brace in what proved a comfortable win over plucky League Two opposition.
"We have not been scoring enough goals," Gallen told the club's official website. "For Darius Henderson and Harry Kane – a new partnership – to score five is good going.
"We put in a good performance and didn't concede which is important too."
Henderson put the home side in front after just seven minutes with an impressive finish after John Still's Dagenham threatened early on, but Gallen admitted it wasn't all plain sailing.
He said: "It was a bit of a nervous start for the opening three or four minutes, but Darius showed his quality with what effectively was probably a half-chance.
"To swivel and find the bottom corner like that was just what we needed really and it settled everyone down so we could go about and play our football.
"We have got to find some first goals in the league because I believe if we can score the first goal, we have the team and the set-up to sit back and hit teams on the break, which teams have done to us.
"I think we are now looking on to Barnsley on Saturday. It was great to get some goals but we are in a perilous position in the league and we have got to do something about it."
Shaun Batt received the biggest cheer of the night after making his return to The Den after over a year out through injury.
"It was great to see him (Batt) back," Gallen admitted. "He can do a bit of everything; he can score a goal, win a header, hold the ball up, make runs in behind, he can link it with his touch and his play and he has a terrific attitude and he is strong as well."