Any reason I can’t use a regular blender in Nigella's recipes when it says to use a stick blender? I refer in particular to the sauce/salsa and soup recipes.
Nigella has many soup and salsa recipes and most just give the instruction to "blend" the soup, meaning you can use either a stick blender or a goblet blender. And for the recipes where Nigella mentions a stick blender it is usually for convenience (less washing up!), such as the Sweet Potato, Ginger and Orange Soup, or because the amount of liquid is quite small.
The one exception is the Golden Garlic Mayonnaise, which needs to be made with a stick blender and a tall, narrow jug, following the instructions carefully. The reason for this is that this method relies on the stick blender blade mixing the ingredients very quickly, helping them to emulsify. But if you don't have a stick blender then you can make the recipe by hand by crushing the garlic to a paste, mixing it with the egg yolk and saffron threads and then whisking the oil in a few drips at a time until it forms a thick mayonnaise.