I’m longing to cook a five-hour beef stew but I feel guilty about how much energy this will use.

I think it’s a smashing idea. With a few minor adjustments to method, there’s no reason to spend any of that lengthy cooking time agonising over your carbon karma.

Forgive me if this shows how dewy-eyed I’ve become about the ways of yester-year, but isn’t this the sort of cooking people used to do? Get all the cooking done on a Sunday and then feast off it for the rest of the week.

So long as you make double quantities and turn your central heating off while it’s cooking, it might even reduce your energy bills. I mention the heating because, with any luck, while your beef is gently tenderising, your kitchen will also become toasty.

And you’ll have a supply of nosh that will need only a short blast of the oven to heat up at each meal. If anyone in your household complains that they’re bored with beef stew, you can give them the lecture about why choice isn’t always a good thing if it means ending up with cheap, lower-quality food (it’s the same one that I use for why we should buy fewer clothes). Better to have the same good-quality beef several times than pick and choose between any number of ready meals.

A kinder way might be to turn the beef stew into an array of exciting risottos and soups, by adding rice, extra vegetables and pulses such as lentils or pearl barley.

This energy-efficient approach to cooking used to define the British kitchen. My mother passed on to me the importance of making the most of a hot oven with her regular cry of “Quick! make meringues, before the oven cools”. Should you wish to do just that and pile other things into the oven that are happy to cook at a low temperature, remember that you may need to increase slightly the cooking time of the stew (to make up for sharing heat).

You recently wrote that we shouldn’t be recycling plastic milk bottle tops. Our council tells us it will accept them.

It may accept them but the tops are not actually recycled. Stuart Foster, project manager at the waste charity Recoup, told me that the plastic industry does not want to discourage people from bothering to recycle plastic bottles. They prefer to separate the tops from bottoms later down the line. While this may seem to be a peculiar attitude, it does makes sense. The machinery at most plastic reprocessing units is now sophisticated enough to filter out bottle tops quite easily, and people can be put off recycling easily by fiddly detail.

I’m afraid that even when the tops are made from the same plastic type as the bottle (often high-density polyethylene), as some of you pointed out that yours were, they will be recycled only if the plastic reprocessor doesn’t mind the impact of their colour.

Green and blue tops, for instance, have an impact on the shade of the final plastic product that is not always welcome. In which case, it’s back to square one, and they are treated as contaminants and dumped.

Don’t take any notice of the triangle and number system marked on the top — that seems to be a promise of eco-status, says Foster. “It is for identification only and does not necessarily denote that a product is recyclable.”

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