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

Input: Consider Input: I usually throw away the remaining water in the electric kettle before refilling it if the water is more than about a day old. In theory wouldn't boiling kill any impurities the old water might have? How long would the water stay drinkable in the kettle (assuming you boil it again before drinking)?

Output: Is it safe to reheat old water in an electric kettle?


Input: Consider Input: Most recipes for sponge cake use a quantity of yogurt which sometimes is replaced with milk, or even soja or almond drinks. In those recipes (flour, sugar, eggs, butter/oil, yogurt/milk, some flavouring), what is the role of the dairy product? Is it about protein/fat/chs, about water, about flavour, about colour? Do the substitution for soja or almond drink make sense, or exist better ones?

Output: What's the role of milk or yogurt in sponge cake?


Input: Consider Input: I really enjoy cooking eggs for breakfast, and sometimes I'm feeling fancy enough to add veggies into my scramble. However, I'm never sure how to prepare the veggies to put into the scramble. If I don't cook them, usually they are too crunchy or tough (and sometimes make the scramble watery), and don't taste good with the eggs. If I try to cook them before adding them, they usually come out too dry/overdone. I figure this might depend on which veggies I'm cooking so here are my common favorites: tomatoes, bell peppers, mushrooms, onions (suggestions welcome!)To make my question more specific (and hopefully more answerable): how can I prepare the veggies so that they are not crunchy, but not over-cooked?


Output: Proper preparation of veggies for an egg scramble


