In a large pan and over a low heat, dissolve the sugar in 100ml of water.
200 g golden granulated sugar
Bring to the boil and "watch like a hawk" until the mixture caramelises. It will take several minutes, but be careful not to let it burn. You're looking for a dark golden colour.
In a separate pan, bring the cream to a near boil then add to the caramel and stir until smooth. If you don't warm the cream first the caramel is likely to seize. If this happens, just keep stirring hard and eventually it should become smooth.
180 ml double cream (heavy cream)
Add the vanilla and salt then stir well. Leave to cool whilst you get on with the cakes.
1 tsp vanilla extract, ½ tsp sea or rock salt
Cakes
Cream the butter and sugar together until light and fluffy.
140 g unsalted butter, 125 g light muscovado sugar
Beat in half the caramel.
Break in the eggs one by one and beat well.
2 large eggs
Sift in the dry ingredients and stir until just incorporated.
125 g flour, 30 g cocoa powder, 1 tsp baking powder, 1 pinch bicarbonate of soda (baking soda)
Spoon into 12 cupcake cases and bake at 180℃ (350℉, Gas 4) for 20 minutes or until well risen and the tops are firm to the touch.
Turn out onto a wire rack to cool.
Buttercream
Cream the butter and icing sugar together until it's very light and fluffy.
85 g salted butter, 125 g icing sugar
Beat in the remaining caramel.
Spread on top of the cooled cakes and decorate with chocolate if you like.
Notes
Please note: calories and other nutritional information are per serving. They're approximate and will depend on exact ingredients used.