2) Cream the butter and sugar in the bowl of an electric mixer fitted with the paddle attachment for about 5 mins, or until light and fluffy. Add the eggs, 1 at a time, then the orange zest.
3) Sift together the 210g of flour, the baking powder, bicarbonate of soda and salt in a large bowl. In another bowl, combine the orange juice, buttermilk and vanilla.
4) Add the flour and buttermilk mixtures alternately in thirds to the creamed butter, beginning and ending with the flour. Toss the chocolate with the 1 tsp of flour and add to the batter.
5) Pour the batter into the moulds, smooth the tops, and bake for 30 mins, until a cocktail stick inserted into the centre comes out clean. Let the cakes cool in the moulds on a wire rack for 10 mins.
6) Meanwhile, make the syrup. In a small saucepan over a medium/low heat, cook the sugar with the orange juice until the sugar dissolves. Remove the cake from the moulds, put them on a rack over a tray and spoon over the orange syrup. Allow the cakes to cool completely.
7) For the ganache, melt the chocolate, double cream and coffee in a heat-proof bowl over a pan of simmering water until smooth and warm, stirring occasionally. Drizzle over the top of the cakes.