Grease a non stick square pan with butter and keep it aside.
In a thick bottom pan, take the condensed milk, add the cocoa powder, whisk it well to make sure you get a lump less mix.
Put it on the stove, keep stirring constantly to make sure the bottom doesn't get burnt.
Add the sugar, continue stirring. Let it melt and get mixed well.
Measure the butter at room temperature and add slowly and continue mixing. As you will see the butter will be all incorporated into the condensed milk.
Continue till you are done with all the butter and the mix starts leaving the sides.
At this stage add the liquid glucose and mix well. Immediately pour over the greased pan. Pat down the pan, so the mix gets evenly spread. If you use any spoon or knife, you will not have that smooth surface. If needed, you can use greased knife to evenly spread.
Allow it to cool down before cutting into pieces. You can even refrigerate to aid the cooling.
I didn't add any nuts as my kids don't eat. But, you can add slivered almonds, raisins, cashews just before pouring the mix or decorate with nuts.