Grease 10 mini loaf tins or sections of a loaf tray, each with a capacity of about 60 ml (2½ fl oz).
Cook the sweet potato in a small saucepan of boiling water for 10–15 minutes until just tender. Drain and mash. Leave to cool.
Put the butter, sugar, vanilla extract, egg and sweet potato in a bowl, sift in the flour, cinnamon and baking powder, and beat with a hand-held electric whisk until smooth and creamy. Divide among the tins and place on a baking sheet. Scatter with the flaked almonds.
Bake in a preheated oven, 160°C (325°F), Gas Mark 3, for about 20 minutes until just firm to the touch. Leave in the tins for 5 minutes, then transfer to a wire rack to cool.
Melt the white chocolate (see