Seated in the dappled shade of an almond tree on a bend of the Douro river in northern Portugal among the terraced vineyards of the surrounding hills, it is hard to imagine anything that could add to the pleasure of a glass of vintage port.

But Rodrigo Nogueira da Silva, resident oenologist at the Vintage House Hotel’s Wine Academy at Pinhão in the heart of the Douro valley, has found an ideal complement in what many believe to be the perfect food: chocolate.