Heat the oven to 180C/160C fan/gas 4 and line the bases of two 20cm cake tins with baking parchment. Beat the butter and sugar together using an electric whisk until light and fluffy, about 2 mins. Add the spread and beat again to combine.

Combine the yogurt, eggs and vanilla in a jug, then add this along with the cinnamon, flour and a pinch of salt. Beat for 1-2 mins until combined. Divide between the tins, level the tops using a spatula and bake on the middle shelf of the oven for 30 mins until risen and golden, or a skewer inserted into the middles comes out clean – if any wet batter remains, bake for 5 mins more, then check again. Leave in the tins for 15 mins, then turn out onto a wire rack to cool completely.

For the icing, beat the butter, half the sugar and all the spread together using an electric whisk until smooth. Add the rest of the sugar and beat again. Warm the caramel in the microwave for 30 seconds to loosen. Sandwich the two sponges together using half the icing and a drizzle of caramel, then spread the rest of the icing over the top and side. Drizzle over the rest of the caramel and sprinkle over the crushed biscuits. Will keep in a cake tin for up to four days.