Cool until needed. To make the frosting, cream the butter with 150g/5½oz salted caramel and the vanilla in a free-standing mixer fitted with a paddle attachment for 3–4 minutes, or until soft ...

Transfer to a wire rack to cool. To make the buttercream, beat the butter using the paddle attachment in a stand mixer or in a large bowl with a handheld mixer for 1 minute. Add the icing sugar ...