Make the pastry. Cream together the butter and sugar, then add flour and almonds. Bring everything together with the egg. If the pastry is very soft, chill for 20 mins. If not, roll out to fit a deepish 23cm fluted flan tin; if the pastry
breaks, press scraps of pastry into the gaps, leaving a slight overhang. Chill for 20 mins.
Heat oven to 200C/fan 180C/gas 6. Line the case with baking parchment and baking beans, then bake for 10 mins. Remove beans and cook for another 10 mins until golden.
Meanwhile, toast the nuts in a dry pan until starting to brown. Scatter over 4 tbsp of sugar, cook until it caramelises, then tip nuts onto a baking tray lined with parchment. Leave to cool, then roughly chop. Over a pan of barely simmering water, melt the chocolate, butter and alcohol together, then set aside to cool slightly. Over the same pan, beat the egg, yolks
and remaining sugar until pale and fluffy. Take off the heat, then fold in the chocolate mix.
When case is cooked, remove from oven and turn the heat down to 160C/fan 140C/gas 3. Scatter most of the hazelnuts over the base, then tip in the chocolate mix, pressing it down slightly. Cook the tart for 15-20 mins until the chocolate has almost set. Leave to cool, then serve scattered with the remaining nuts. Can be made up to 1 day ahead.