Put 100 grams butter/margarine, 200 grams of syrup, 30 grams cocoa in a large saucepan.
Warm gently over heat whilst stirring until the chocolate syrup mixture is smooth.
Tip in 200 grams cornflakes.
Stir gently into the chocolate syrup. It does take a little time to coat all the flakes. Stay strong.
Empty into your tin or dish. I use a deep 8 " loose bottomed square tin but you could use a bit bigger or smaller tin. The smaller you go the thicker the cracknell and vice versa.I recommend lining the tin with baking or greaseproof paper just so as to be able to get it out super easily.
Press firmly down with a metal spoon and level the cornflake mixture flat.
Chill in the fridge for at least 3 hours.
Cut into required shapes with a sharp serrated knife
Notes
Use the golden syrup from the tin not squeezy bottle. The syrup in the bottles is more liquid (pouring) than the original golden syrup in the tins.
Use the freezer to speed up the setting process.
They are better kept in the fridge. If they get too warm they can fall apart a bit.