Heat oven to 180C/160C fan/gas 4. Line 2 x 20cm loose-bottomed Victoria sandwich cake tins with baking parchment, then grease one of the tins over the top of the parchment (this will help to prevent the caramel-nut topping from sticking when you turn it out).
Tip the nuts into a frying pan and toast over a medium heat until golden. Add 50g of the butter, 50g sugar, the golden syrup and a good pinch of salt. Stir until the butter has melted, then bubble for 2 mins until the buttery sauce is golden brown – don’t let it bubble for too long or the topping will set hard once cooled. Tip into the cake tin with the greased parchment and smooth over. Leave to cool while you make the cake.
Tip the remaining butter and sugar into a large bowl and beat with an electric whisk until pale and fluffy. Add the eggs, one at a time, mixing well between each addition. Add the flour, almonds, baking powder, 1⁄2 tsp salt, almond extract and milk, and mix again until just combined. Divide the cake mixture between the tins and smooth over the surface. Bake for 25 mins, or until a skewer comes out clean. Leave to cool in the tins for 10 mins, then flip out onto a wire rack and remove the parchment. Allow to cool completely.
Whisk the cream and 2 tbsp of the caramel until softly whipped and just holding its shape. To assemble the cake, place the plain cake on a plate or stand. Top with the whipped cream, swirling it out towards the edges. Drizzle over the remaining caramel (give it a good mix first to loosen it), letting it dribble down the sides. Top with the remaining sponge, nutty-side up. Serve within 1 day, or store in fridge for 3 days, removing it from the fridge 10 mins before serving.