Mix the crushed biscuits with butter and press into an 8" loose bottomed tin and chill. Melt the chocolate over a pan of boiling water or 2 minutes on high in the microwave oven. Blend the cheese with sugar, egg yokes and yoghurt. Blend in the chocolate. Whisk the egg whites then fold them in. Pour the mixture over the biscuit base and level with a palette knife. Make small furrows round the edge and chill until completely set. (Fairly soft). Remove from the tin and decorate with whipped cream and orange segments. Scatter zest on top. If using chocolate curls gently press them round outside of cheesecake.

Mix all the ingredients together well.

Line and oil a 2 lb loaf tin. Mix all the ingredients together and then press into the tin and level the surface. Cook for 1 hour and 30 minutes at Gas mark 4 or 350°F then cool slightly. Press by standing a board or plate on top of the mixture with heavy object on it to hold in place. Leave to cool completely.