We have a recipe for a salted caramel spread that is basically a big pan of sugar, glucose, milk and butter, cooked until it becomes a thick paste, then mixed with double cream to achieve a smooth consistency and a glossy finish. Our only problem was that we kept having big variations between batches -- some ended up as thick, sticky spreads (like we intended), others were runny and sauce-like.
After some experiments we discovered that the final stage of the process -- pouring the double cream in -- was responsible. Pour the cream cold and the caramel would come out runny; heat the cream before pouring and the final result would be thick and rich.
Although we feel we're in control of the process now, I was wondering if anyone could explain to us why does heating or not heating the cream have such a big impact on the thickness of our spread.