Place the sugar in a deep and heavy bottomed saucepan, place over a medium heat and let the sugar dissolve and turn golden brown without stirring the pan. This helps prevent the caramel from crystalising.
Whist it is dissolving, heat the cream in another saucepan and bring to a boil
Being very careful, pour half of the cream into the hot caramel, let the bubbles fade away and then stir fully. Repeat with the other half of the cream.
Bring it back to a simmer and cook it down for a few minutes to thicken the caramel. Once it’s is a lovely deep brown colour and slightly thicker, take off the heat and stir in the cold butter cubes and salt. Finally stir in the 1tsp of Biscoff or seed butter
Pour into a clean jar and leave to cool.
Place in the fridge and this will thicken nicely to a thick caramel spread