Base: In a medium bowl combine biscuit crumbs, almonds, sugar and melted butter. Mix well. Press into the bottom and halfway up the sides of a 25cm springform pan.
Filling: In bowl over boiling water heat the chocolate stirring occasionally until it is melted and smooth. Remove from heat and allow to cool to lukewarm.
In a large bowl beat the cream cheese and sugar until smooth. Beat in the eggs one at a time. Fold in the almond essence and sour cream. Pour 1 1/2 cups of the filling into a smaller bowl. Stir the melted chocolate into the smaller bowl then fold loosely back into plain filling. Pour into crust. With the tip of a knife swirl the filling to create a marbled effect.
Bake in the preheated oven for 40 minutes. Turn off oven and let cake cool in oven for 1 hour with the door closed. Cool at room temperature then refrigerate overnight.