142 ml of sour cream is a very specific amount in the Chocolate Guinness Cake recipe. Why is this?
Nigella's Chocolate Guinness Cake (from FEAST) was originally written by Nigella many years ago and at the time in the UK in supermarkets the size of a small pot of sour cream was 142ml as this was the exact metric conversion of ¼ pint. Hence the measuremant of 142ml was used in the recipe.
This has evolved over time and now in the UK the container has changed to 150ml. The difference is small (just under 2 teaspoons) and will not affect the cake and we have updated the on-line recipe accordingly. The US measurement of ⅔ cup stays the same.