Salted Chocolate Tart Soft Centre

Our answer

Nigella's Salted Chocolate Tart has a filling that is flavoured with chocolate and coffee. It is made with double cream (or heavy or whipping cream) and usually a regular thickened cream will have a high enough fat content, although if it is a low fat thickened cream then this could have affected the mixture. You should also use chocolate with a high cocoa content (if possible 70% cocoa solids). The filling is thickened with cornflour (cornstarch) and this activates as the mixture is heated. As the tart filling contains chocolate you should not actually boil the filling, but after about 10 minutes of cooking the mixture is usually thick enough to set. We don't think that the induction hob would have affected the method but the heat level used may have been a little too low. If you are unsure you could heat the cream, coffee and cocoa together then add the cornflour paste and bring this mixture to the boil, stirring constantly. After this remove the pan from the heat, cool slightly and then stir in the finely chopped chocolate until it has melted and the filling mixture is smooth. Try not to incorporate too much air while stirring the filling as it will create bubbles, which can spoil the appearance of the tart.

If you have a food processor with a smallish bowl then you can process the chocolate and cookies in two batches then transfer the crumbs to a bowl. Melt the butter and stir this into the crumbs until it is evenly distributed. It can also help to roughly break up the cookies before putting them into the food processor bowl.