Line a baking tray with non-stick "baking paper". This is a different thing to greaseproof paper, and is worth the slightly inflated price. In a food processor (or using a blender/stick blender if, like me, you don't have one), grind together the icing sugar and ground almonds until lumpless - you want them as powdery as you can.
In a large bowl (don't use plastic), whisk your egg whites, food colouring and caster sugar. It helps to own an electric whisk. It might take a while, but they will eventually become filled with air and quite stiff, though it doesn't matter if you quite reach 'stiff peaks'.
Add about half your sugary almond powder to your airy sugary egg whites and very, very carefully 'fold' together with a large, metal spoon. This just involves gentle mixing, making sure you scoop from the bottom, in order to keep the air in.
Add the rest of your powder. But here's where making macarons will blow the mind of an experienced meringue maker - it's time to mix everything well. You want to force most of that air you've captured out so that the mixture, gradually but gloopily, tumbles from your spoon. Stop when it reaches exactly the consistency of flowing lava - when you drop some into your bowl, the surface should slowly flatten out to leave no visible peak. This might well be looser than you were expecting.
If you own a piping bag, great. If not, a freezer or sandwich bag is just as good. Scoop your mixture into your bag and twist the open end to force the mixture into a corner. Cut this corner off using scissors, leaving a hole about 1cm wide. Use this to squeeze little circles onto your prepared baking sheet. You want them anything between 1-2 inches in diameter. Leave plenty of space between each one.
Once your macarons are piped, lift your baking tray about a foot or two above your work surface, and drop it so it smashes down dramatically. Repeat 2-3 times - it's just to remove any big bubbles that might be left in the mixture.
This is the most important step. Leave your piped macarons, uncovered and at room temperature, for AT THE VERY LEAST 30 minutes. The longer the better. You want the surface to dry out and a skin to form. At this point, preheat your oven to 180C/160C fan - fan is better. Your oven must be properly per-heated for at least 30 minutes.
Bake for between 10 and 12 minutes, depending on the size you've gone for. You must take them out before they begin to go brown. A good tip is to open the oven fully, then quickly close it again, at least twice during cooking. This removes excess steam.
Once baked and cooled, remove from the tray, spread the underside of half of them with jam and sandwich together with the other half. They are best enjoyed at least 1 day after assembly, as they soften and absorb the flavours of the raspberries over time.
Clean your oven. The first time I ever made macarons, they ended up tasting like porky fish because we'd had fish for dinner two days previously and pork the night before. Anything with egg whites tends to absorb the aromas around it. Give your oven a really thorough scrub before you start - its a good excuse!