Cadbury's historic Bournville base will continue to be the home of its famous Dairy Milk bars following a £75 million investment.
Owner Mondelēz International has spent the past few years installing four new lines at the factory in south Birmingham which means production of certain bars which temporarily shifted to Poland is now coming back to the city.
Two of the new lines are dedicated to retaining Bournville as the home of Cadbury Dairy Milk where it will produce bars such as Caramel, Fruit and Nut, Whole Nut and plain.
The other two new lines will create assortments boxes such as Roses and Heroes which the company said was the first significant investment in Cadbury's assortments for 30 years.
US giant Kraft bought Cadbury for £11.5 billion in 2010 and the decision was taken subsequently to shift manufacturing of some products from Bournville to Poland temporarily to allow the new lines to be installed.
These are now coming back to Birmingham while there are also plans afoot to add further bars from the Cadbury range to the Bournville production lines.
Work to implement the new lines started in 2014 and now the Dairy Milk tablet lines produce up to eight tonnes an hour, making 900,000 200g bars or 1.2 million 110g bars per day.
The Roses and Heroes lines produce up to six tonnes an hour, making 13 million sweets per day.
Glenn Caton, president of Northern Europe at Mondelēz International, said: "This £75 million investment we've made means our Bournville factory can now favourably compete against manufacturing facilities in other European markets and retain the majority of Dairy Milk and chocolate production right here in the UK.
"Previously, it cost three times more for us to make a chocolate bar here in Bournville than it did in Germany. That wasn't sustainable.
"That's why our investment in these world-class production lines is so vital.
"In total, we have invested £200 million in our manufacturing operations and R&D facilities across Britain to ensure we continue to make the nation's favourite treats in the UK for years to come.
"Our Bournville factory is not only an integral part of a thriving, modern British manufacturing sector, it is the home of Cadbury and heart of chocolate manufacturing to our global business."
The factory in Bournville opened in 1879 after George and Richard Cadbury moved manufacturing from the centre of Birmingham.
It has an R&D team and innovation kitchen meaning that every Cadbury product sold starts life in Bournville.
There are now a total of 21 manufacturing lines at the site making products such as Giant Buttons, Wispa, Easter egg shells, Caramel nibbles and Caramel eggs.