STEP 1 Heat the oven to 180C/160C fan/gas 4. Line a 12-hole cake tin with paper cases.
STEP 2 Beat the butter and sugar together with an electric whisk until pale and fluffy. Add the eggs, one at a time, and the vanilla extract. Briefly mix in the flour until just combined, and stir in the milk until the batter just falls off the beaters.
STEP 3 Divide the mixture between the cases, leaving about 2 tbsp batter in the bowl. Add a pinch of salt to the caramel sauce if it’s not salted caramel, then add ½ tsp to the tops of each cupcake. Use a teaspoon to cover the caramel sauce with the remaining batter. Bake for 15-20 mins until springy and golden. Leave to cool completely on a wire rack.
STEP 4 Meanwhile, make the icing. Beat the butter and half of the icing sugar together, then tip in the remaining icing sugar and whisk vigorously until pale and fluffy. Stir in half of the caramel sauce, then spoon the mixture into a piping bag with a round or star nozzle.
STEP 5 Pipe swirls of icing on top of the cooled cupcakes. Stir the remaining caramel sauce with a pinch of salt, if unsalted, then use to drizzle over the icing. Sprinkle over a small pinch of sea salt over each, if you like.