Given the background description of some cooking related query, summarize the question into a title

Example Input: When making a peanut butter based sauce, how can I loosen the peanut butter and even out the consistency ? I tried adding a bit of hot water and mixing them, but even after simmering for a while in the pan with frequent stirring I still found clumps of peanut butter.
Example Output: How to loosen peanut butter in a sauce

Example Input: In Masterchef The Professionals (season 8 episode 11), Marcus Wareing demonstrates his skills test and cooks a burger. In the process, he rapidly cools the onions after sweating them by placing them on a freezing tray. Would it make a noticeable difference to skip that step? I never did this and my burgers did not fall apart as he suggests. Is there some other reason for doing this?You can see the episode here (skip to 17:30).
Example Output: Cooling cooked onions before adding to raw mince

Example Input: My local supermarket was out of 1% milk today, so I decided to get half a gallon of 2% and half a gallon of skim milk and combine the two at home. Now I'm wondering in what I should store the combined milk...I still have a 1 gallon container from the last milk I purchased which I can use. There's a tiny bit of milk left in there, but it will be finished by today. The only thing I'm worried about is that, even if I wash the container the best I can, it will still have traces of bacteria in there from the old milk. Does this mean, then, that I should treat the expiration date of the combined milk as the same date printed on the old container?Should I store the milk in some other container (e.g. a pitcher)? Should I temporarily combine the two in a pitcher, then put them back in the two half gallon containers they came with? Any other ideas?
Example Output:
Which container to use for combined milk?