Method

• 1.
  Preheat oven to 180°C/160°C fan-forced. Line a baking tray with baking paper.
• 2.
  In a stand mixer fitted with the paddle attachment, beat the butter, sugar and egg yolk on medium-high speed until well combined. Sift over flour, cocoa and baking powder and beat on low speed until just combined. Add hazelnuts and beat until just mixed through. Divide into 12 portions and roll each into a ball.
• 3.
  Place a 6.5cm-wide heart-shaped cookie cutter on the prepared tray. Place a ball in the cutter and press down with your thumb to flatten out and fill the shape of the cutter. Remove cutter and repeat with remaining portions.
• 4.
  Bake cookies for 10 minutes. Immediately, while cookies are still hot, use a teaspoon or your fingers to imprint a heart-shaped cavity in the middle of each. Heat Nutella in a microwave in 30-second bursts until runny and smooth, then spoon into each cavity. Set cookies aside on tray to cool completely.
• 5.
  For the Swiss meringue, whisk all ingredients and a pinch of fine salt in a large heatproof bowl. Place bowl over a saucepan of simmering water (don’t let base of bowl touch the water). Whisk constantly until mixture is white, doubled in volume and all sugar is dissolved (when you rub mixture between your fingers, you shouldn’t feel any grains of sugar, and it must feel hot). Transfer to a stand mixer fitted with the whisk attachment. Whisk on high speed for 2-3 minutes, until stiff peaks form. Divide between 2 piping bags, one fitted with a 1cm star nozzle and one fitted with a 1.5cm ribbon nozzle.
• 6.
  Pipe decorations onto cookies. Use a kitchen blowtorch to caramelise the meringue. Serve.