boiling + poaching eggs
Unless you buy them directly from a farmer, it's difficult to know accurately how old your eggs are. You're left with the glass of water method and the 'best before' date. For the former, put an egg in said liquid; if it lays completely horizontally then it's very fresh; if completely vertically, then it's stale. That's the idea, anyway. I tend to go by the 'best before' date. This may be up to a maximum of 28 days after the eggs are laid (although eggs can be edible up to eight weeks after laying). At the supermarket, rather than choose large, medium or small, I rifle through the boxes in search of the furthest away 'best before' date. The age of your eggs is most crucial when you're attempting to poach them (see below).
I always prick the larger end of the egg with a pin before boiling, to prevent the shell cracking. The methods below are for medium eggs.
Soft yolk, barely set whites: Bring to a simmer enough water to cover the eggs by around 100ml. Lower in the eggs and simmer for one minute. Remove from the heat, cover with a lid and leave for six minutes.
Firmer yolk, completely set white: Same as above but leave for seven minutes. This gives you an oeuf mollet - a (carefully) peeled egg that can be laid on top of (say) a salad and cut open so the yolk oozes out gently.
Hard boiled: Place in cold water. Bring to a simmer and cook for seven minutes. Run under a cold tap for a minute or so.
Few things are more guaranteed to turn your morning to shit than the site of the whites of your eggs separating from the yolks and turning into an evanescent cloud. Which is why people buy those naff poaching pans - the cooking equivalent of the tartan shopping trolley. There's really no answer other than using really fresh eggs - vinegar may be partly effective, but can affect the flavour of the eggs. Some suggest making a cling film pouch for each egg. Yeah, right. However, assuming you have fresh eggs:
Have a pan of barely simmering water and a bowl of ice cold water ready. Crack an egg into a small cup or ramekin. Whisk the water into a whirlpool effect and carefully lower the egg into the centre. When set, after about 3 minutes, lift out the egg and slide into the bowl of icy water. Repeat with your chosen number of eggs. You can trim the whites if you want for a neater effect. To serve, simply reheat for 30 seconds in a pan of simmering water.