The record-breaking baking took place last week during the Rotary's Cafe holiday club run at the Whole Life Christian Centre in Cabin Lane.
After two days of making the enormous mixture for the biscuit the 55 children who took part found out they had broken a world record on Friday.
The finished biscuit measured 68cm x 50cm x 6cm and weighed 16.3kg (2st 8lbs) – beating the previous record, held by a chef in Nottingham since 2010, which measured 59cm x 39cm x 6.5cm and weighed 15.7kg (2st 6lbs).
Jason Fell, who has been coordinating the holiday club for the past five years, said the youngsters had been thrilled.
"When we announced that we had taken the record there were huge cheers from the children and all the helpers. They were very excited that they were the first to eat a world record making biscuit."
"I looked into world records and I saw that a giant custard cream could be a possibility."
Hannah Guntrip, who runs Han Made Cakes in St Martins, took charge of creating a recipe and overseeing the baking. The children did the mixing and making on Tuesday and on Wednesday the biscuit was put together. They had to use an oven at Moreton Hall School, near Oswestry – the only one big enough.
Mr Fell said there was almost an eleventh hour disaster. "The edge of the biscuit was beginning to collapse. Hannah had left to travel to the airport for a holiday in Canada. But when we asked her advice she came back and whipped up another kilo of cream for inside."
The biscuit was broken up into smaller pieces at the event on Friday and sold to raise funds for the Derwen College in Gobowen.