1. Preheat oven to 180°C/160°C fan forced. Grease a 20cm round cake pan; line with baking paper. Stir 120g of the chocolate and coffee in a small saucepan over very low heat until melted and smooth. Cool.

2. Beat 125g of the butter with sugar until light and creamy using an electric mixer. Beat in egg yolks until blended. Stir through flour, then hazelnuts. With clean beaters, beat egg whites to soft peaks; fold through batter with chocolate mixture. Spread batter into prepared pan.

3. Bake for 25-30 minutes until cake begins to pull from edges but centre appears slightly moist. Turn off oven, leave door ajar. Cool cake in oven for 10 minutes. Remove from pan; turn upright on a wire rack. Carefully spread top with jam; cool completely.

4. Melt remaining chocolate in a microwave-safe bowl on High (100%) in 20-second bursts, stirring until smooth. Stir in remaining butter. Cool, stirring occasionally until mixture begins to thicken. Quickly swirl over cooled cake, letting it drip down sides. Garnish with hazelnuts. Allow coating to set before cutting.