Blend almonds until bready and crumbly. Blend oranges until smooth. Beat the eggs and sugar until pale and add other 3 ingredients. Mix well and bake in a buttered tin at 225 °C for just over an hour, or until a skewer comes out cleanly.
Meanwhile, boil all the syrup ingredients until dissolved and slightly thickened. Serve with the syrup cold and some mascarpone cheese or thick cream.
