- Preheat the oven to 180°C/gas mark 4. Line a large baking sheet with non-stick baking paper and set aside.
- Place the butter in a medium pan with the just-boiled water and cook over a high heat until the butter has melted and the mixture is bubbling fast. Add the flour and beat thoroughly with a wooden spoon until the mixture is smooth and forms a ball in the centre of the pan. Remove from the heat and leave to cool for 1 or 2 minutes. Beat the eggs in a small bowl, then add them a little at a time, beating vigorously, until well combined and with a good sheen. You may not need all of the beaten eggs – use just enough to give a piping consistency.
- Spoon the mixture into a piping bag fitted with a 1cm plain nozzle. Pipe 12 x 7cm lengths, about 2.5cm wide, spaced well apart, on the prepared baking sheet. Use a wet knife to cut off the pastry neatly at the nozzle.
- Bake in the oven for 20 minutes, until puffed, crisp and golden. Remove and lower the oven temperature to 160°C/gas mark 3.
- Meanwhile, whip the cream to soft peaks and set aside.
- Using a sharp knife, split the éclairs open through their side and down their length to begin opening them out like a book. Return to the oven for a further 5 minutes to dry out the insides. Transfer to a wire rack and leave to cool completely. Once cool, spread the Nutella inside on the base, then pipe or spoon in the whipped cream and sandwich back together. Return the éclairs to the wire rack and set the rack over a tray.
- To prepare the topping, sift the icing sugar into a medium bowl. Add the water and a small dot of food colour and mix to give a smooth, slightly runny glaze. Add more food colour for more intensity if liked. Working quickly, stirring often to prevent it from forming a crust, spoon a heaped tablespoon of the glaze on top of each éclair, spreading it with the back of the spoon. Arrange three raspberries upright on top of each one and a sprinkling of hazelnuts to stick to the glaze before it sets. Arrange on serving plates, a platter or cake stand and serve at once.
Tip: For a healthier option, fill with natural yogurt and fruit pieces and drizzle the tops with a little melted dark chocolate (at least 70% cocoa solids). The hazelnuts are even more delicious if roasted first. Simply tip the whole nuts onto a baking tray and roast in the oven at 180°C/gas mark 4 for 10 to 12 minutes, until golden. Immediately tip into a clean, damp tea towel, wrap them up in it and rub briskly for a minute. This should remove the skins to reveal the roasted nuts.