Is the cornflour used in the Yogurt Pot Cake what we in Canada call cornstarch? Cornflour here is yellow and kind of grainy. Please clarify for me. Thank you.
Nigella's Yogurt Pot Cake (from NIGELLISSIMA) is made with a combination of plain (all-purpose) flour and cornflour. The cornflour is added as it has no gluten and helps to make the cake more tender and crumbly. Cornflour is very refined and finely milled and in the US and Canada is usually labelled as cornstarch (in French it would be labelled as fécule de maïs or maïzena). For the US versions of ingredients for Nigella's on-line recipes you can use the "metric to cups" toggle at the top right hand side of the ingredients list. Slide the toggle to the right to see the conversions.
You can use potato starch as an alternative to the cornflour. Potato starch was the traditional Italian ingredient in the cake, but in most places cornflour/cornstarch is easier to find. Potato starch is also a fine white powder and not to be confused with potato flour, which is usually coarser/granier.