For Nigella's Chocolate Peanut Butter Cheesecake one of the ingredients is sour cream, but the measurement is in mililitres. The problem is that the sour cream is not completely liquid (I did leave out to get to room temperature) so I could not put into a measuring jug. Can you give any advice regarding converting mililitres to grammes if the ingredient is not completely fluid, e.g. sour cream or cream cheese? Thanks
For metric measurements liquids can be easily converted to weight as 1 millilitre of water weighs one gram, so 100mls water will weigh 100g. This relationship can change slightly for more dense liquids but fortunately for sour cream the difference is so slight that you can convert to grams from the volume. So in Nigella's Chocolate Peanut Butter Cheesecake (from Kitchen) you can use 125g sour cream as this is the same as 125mls sour cream. The cream cheese is given by weight anyway (500g).
If you have a set of measuring cups then it is easier to measure the volume as you can spoon the cream into the cup measure and scrape it out again. 125mls is the equivalent of 1/2 cup.
You can also measure yogurt, single and double cream, creme fraiche and milk by weight, substituting grams for millilitres. Cream cheese and mascarpone are more dense so there is a slight difference and the weight is usually about 5% less than the volume. But for many recipes this difference is small enough not to matter too much. Items like golden syrup and honey are more dense so cannot be converted from volume to weight so easily.