Spread the nuts on a baking tray and roast them in a preheated oven (electric cooker: 175 °C/ circulating air: 150 °C/ gas: see manufacturer) for approx. 8 minutes, take them out and place them on a flat plate covered with baking paper.
Let it cool down. Coarsely chop 2/3 of the nuts. Boil down the sugar and 2 tablespoons of water in a pan to a golden brown caramel. Pour over the nuts immediately and let them cool down.
Coarsely chop the milk chocolate and melt it with 100 g butter, 50 g cream and 1 tablespoon syrup over a warm water bath while stirring. Coarsely chop dark chocolate as well and melt with the remaining butter, cream, syrup and cinnamon while stirring occasionally.
Remove both mixtures from the water bath. Stir one half of each chopped nut into the chocolate mixture and let it cool down for about 20 minutes.
In the meantime, cut off a long strip of baking paper about 10 cm wide. Place it in a box mould (8 x 25 cm) so that the ends look over the edge of the long side of the mould. Fill both chocolate masses alternately spoon by spoon into the mould and smooth them down.
Cover and leave to cool for approx. 1 hour. Remove the terrine from the pan with the help of the baking paper strip and turn it over onto a cake plate. Decorate with the caramelized nuts.