I followed the Flourless Chocolate Brownies recipe and after 30 minutes of baking the brownie mixture had not set. So I continued to bake for 2-3 hours and the mixture was still in liquid form with bubbles on top. I added all ingredients on the recipe except walnuts and almonds as I didn't have them at home. Is that the reason why it has not set?
Nigella's Flourless Chocolate Brownies With Hot Chocolate Sauce (from NIGELLA EXPRESS) are made without flour, but this is replaced by ground almonds (almond meal). Unfortunately the mixture does need the ground almonds and this will be the reason why the mixture did not set and become cake-like. We suspect that on cooling the mixture would be quite solid, more like a firm chocolate truffle.
When ground nuts are used they are usually an essential ingredient as they provide structure to a cake and sometimes also additional moisture. So it is difficult to omit them or replace them with regular flour, though sometimes you can replace them with a different variety of ground nuts. Roughly chopped nuts, and other chopped items such as chocolate and dried fruits, are larger than ground nuts and are usually included for contrasting texture or a burst of flavour, so sometimes can be omitted or changed. If you are not experienced in baking then it is best to include all of the ingredients listed for the recipe.