I have a bunch of food storage things I have to post, so I thought I'd share one today, especially since this is on my "to do list" for this week. My brother-in-law had a hugely successful basil crop in his garden (mine - not so good). There are two things I have done in the past to preserve it when it gets to the end of basil season.
Clearly the photo is old, but I keep up the same routine the years I can. Making pesto is a great way to be able to use your garden basil later. Plus, having pesto whenever you want it is awesome.
I have used various recipes and don't really have a favorite. They all usually involve pine nuts, olive oil, and Parmesan. There are tons of varieties using different nuts. Once the pesto is made up, you can just plop big scoops into a muffin tin and then freeze it. It may be easier to pop them out if you use plastic wrap first and then plop in the pesto. That is what I usually do now - and spraying the wrap with cooking spray helps too.
Once each pesto "muffin" is frozen, you can place them all in a freezer bag. Squeeze out any extra air (or close the bag most of the way and use a straw to suck the air out). Now when you need a cup or so of pesto, you have it ready to go. You can also very easily do this with pre-made pesto. Costco sells really big bottles of it that would be pretty hard to go through without preserving some of it like this.
As for a more basic use of basil, you may want to try this. Pick the leaves off the stems and rinse them.
Chop the basil up. I like using kitchen shears to cut slices.
Fill a clean ice cube tray with as much cut up basil as you can. Generally an ice cube size is about 2 tablespoons. So, the more you can pack, the more accurate your measurement later. Some people freeze their basil in olive oil. I just use water. I just pour whatever water will fit over the basil in and then freeze.
They come out looking like this! I pack them up in freezer bags, similar to the pesto and get as much air out of the bag as possible. The basil then can be used where fresh basil is asked for in recipes. You just need the ice to thaw off of it. I usually just put the cube(s) in a strainer and run a little hot water over them. Now, I will say that I would not use this in something like salad where you really do need real fresh stuff. It's great though for pasta, pizzas and other warm foods.
If I didn't explain too well of you have any questions, please ask! Otherwise, get your freezer full of basil. It is way to delicious to just waste away and have wither away!