Is it okay to substitute boiling water with Kahlua in the Chocolate Olive Oil Cake?
Nigella's Chocolate Olive Oil Cake (from NIGELLISSIMA) is a rich chocolate cake that can be made in a gluten-free form with ground almonds (almond meal). The cocoa powder is mixed with boiling water before using. Doing this helps to "bloom" the cocoa, bringing out the chocolate flavour. Cocoa powder is also very absorbent and mixing it with a hot liquid first can prevent the cocoa from making some baked goods too dry.
We don't see any reason why you should not use a coffee liqueur, such as Kahlua, as an alternative to the water. Coffee helps to bring out the flavour of chocolate so the two should go well together. You would need to warm the liquid gently, just to boiling point, before mixing it with the cocoa powder. However please note that not all liqueurs are gluten-free, so check before using if the cake needs to be gluten-free.