Heat slowly over low heat to melt butter and dissolve sugar.
Increase heat a little if necessary to bring to a slow simmer.
Simmer for 20-30 minutes, stirring frequently.
The mixture should thicken and become darker. It's ready when the mixture is a dark, almost chocolate colour and comes away from the bottom of the saucepan as you stir it.
Pour mixture into the greased tin.
Allow to cool for about 10-15 minutes and then score using a butter knife (to create 11 x 7 rows). Once completely cool you can break into small squares along these lines.
Store in an airtight container.
Video
Notes
Storing: Best kept in a cool, dry place (but not the fridge) and should last a week in an airtight container.Freezing: Not suitable.Nutrition: The nutrition information is an automatically generated estimate and is not guaranteed to be accurate.