Hi, can I ask what can I use as substitute for custard powder in the Chocolate Cheesecake? Also can I use unsweetened baking chocolate instead of dark chocolate?
Nigella's Chocolate Cheesecake (from Feast and on the Nigella website) uses custard powder in the filling as this helps to stabilize the filling as it cooks and adds some vanilla flavour. However if you cannot find custard powder then you can use 1 tablespoon of cornflour (cornstarch) instead and add 1 teaspoon of vanilla extract when you add the cocoa dissolved in boiling water to the cheesecake batter.
Nigella uses a dark (bittersweet) chocolate in most of her recipes and in the UK the preference is usually for one with 70% cocoa solids. In the US the level of cocoa solids tends to be slightly lower but you can still use a good quality bittersweet chocolate; look for a bar with cocoa solids of 62% or more. Baking chocolate tends to be almost 100% cocoa and we would not recommend using this in the cheesecake or in Nigella's recipes generally as it unsweetened and so could cause the dish to taste slightly bitter. In addition most eating chocolate contains a natural substance called lecithin which is an emulsifier. This is not usually present in baking chocolate and we are not sure if this chemical difference could affect the texture and cooking of the cheesecake batter.