How do I cook with basil?

I'm starting to use basil more in sweet foods now. I saw Chef Michael Chiarello mince it up and add it to softened vanilla ice cream. I've also had a basil panna cotta that was incredibly delicious.

In addition to pasta sauces (like pesto), you can use fresh basil in salads like a Caprese salad of fresh mozzarella and tomatoes. Or in a plain tomato salad. I use the Asian (anise, lemon, cinnamon scented) basil in my stir-fry.

You might also try making some basil oil for finishing purposes. Simply puree fresh basil leaves in olive oil with a pinch of salt for a bright green "sauce" to garnish summer dishes with. This is great on an insalata caprese, in cold soups, or over pasta. Just be sure not to make a lot at a time--it will keep no longer than a week stored in the fridge. Also remember that if you chop basil and then let it sit for any length of time, it will start to turn an unappetizing brown color. This is why pesto, left uncovered, will turn brown unless it's covered in olive oil. It's an oxidization reaction, which makes me sound like I know something, although I'm not really sure, molecularly, why this happens.
You might also track down some less familiar basil varieties. Globe basil is a smaller plant with smaller leaves, but with a big flavor. Thai basil is redolent of cinnamon and anise. Genovese basil is sweeter. In short, there's an exciting world of basil varieties out there.

Basil's flavor is delicate and can easily cook away, that's why the recommendations to add it at the end. Alternatively you can add some toward the beginning and freshen the flavor at the last minute. It makes a beautiful garnish, especially if you use the top inch or so of a stem (it doesn't bruise that way either).

Thanks for the advice! I wasn't sure if I put it sauce at the beginning cooking (slow cooking) it would get bitter tasting.

Great answers here.

Fresh basil freezes great, fyi, which comes in handy when you happen upon a glut of basil in the summertime. I strip my basil leaves from the branches and lay them in a single layer on a cookie sheet, then freeze. When frozen, quickly transfer to a plastic freezer bag and use when making pasta sauces.

As sarah noted, pesto is delicious: basil, toasted pine nuts, garlic, olive oil, parmigiano and salt. Traditionally made in a mortar it's also perfectly okay to spank it in a food processor. It can be used as a finishing herb too; this past week I cooked julienned zucchini ala minute in olive oil and added chopped basil at the very last moment.

Usually you add basil at the very end of cooking, as a garnish - though in pasta sauces there will be times when you add it at the beginning or throughout. It bruises very easily, and can oxidize (turn brown) so often it's good to tear the leaves into whatever you're making.

As to how much to use, it depends on what you're making - a pesto is made up of 3-4 large handfuls that get pounded into 1/4 of a cup, whereas a margherita pizza may only have 3 leaves. So the best answer is "to taste".