Preheat oven to 180°C non fan forced.

Combine dextrose with 100g of the butter in a medium saucepan, set the other 100g aside.

Place saucepan on medium heat, stirring as the butter melts, and bring to the boil.

Once it's bubbling well, boil for 1 minute, stirring all the time.

Remove from the heat, stir in remaining 100g of butter along with vanilla and set aside to cool. (Put the saucepan in a bowl of tap water to speed up the process.)

To a large bowl add cornflakes, roughly crushing into crumbs with your hands. Add flour and baking powder and stir well with a wooden spoon.

Chop up homemade chocolate into small chunks. You would usually stir chocolate chips into the dough, however the homemade chocolate is soft in texture and would not stand up to mixing. (Of course you could use store bought chocolate -90% cocoa works well, just chop up and add to the flour mixture now.)

Once the butter mixture is at room temperature, add to flour bowl, mixing well.

Assemble 2 large baking trays - no need to grease or line with paper - they won't stick.

Using your hands, roll roughly a tablespoon of mixture into a ball and flatten in the palm of your hands. Push two or three pieces of chocolate into the flattened dough. Add some extra dough on top to cover the chocolate and squash flat with your hands, about 3 to 5mm thick.

Place on the tray close together. The cookies will not spread or rise much.

Bake 180°C for 18 to 20 minutes. Cookies should be light golden. As they bake the chocolate will bubble up and peek out of the dough. 

Lift cookies onto a wire rack to cool.

Store in a jar or airtight container up to 1 week.