Step 1 - cut the basil leaves off your basil bush (or buy some from the store, its much cheaper to grow your own 1.50 at Lowe's!) I read that for everywhere you cut, two basil leaves will grow back on the bush (we're still investigating that claim!). Leave enough extra on the bush to encourage growth, don't hack the whole thing off! It takes about a month for the growth to come back, I've added another basil plant for this reason, so I alternate cutting them back every other month. Then wash the leaves thoroughly and lay to dry on a towel.
Step 2 - place basil leaves in a food processor or blender, add extra virgin olive oil (Costco has a great price 24.00 or so for almost a gallon, it will last a long time!), enough to liquify the mixture. I added 1 cup for every 10 leaves, but it really depends on how much you like basil! You can also add other herbs like garlic cloves to your mixture. Then blend until liquefied.
Step 3 - pour basil mixture into ice cube trays and place in the freezer for 12+ hours. After the cubes are completely frozen empty into a Ziploc bag and date. The cubes should last in a deep freezer for up to a year - by moving them when frozen, the cubes shouldn't't stick together making it really easy to grab a few each time you are baking! Remember the FIFO method - first in first out. Use the oldest date first yo insure you don't have to throw any away due to freezer burn. Then the next time you want to cook with basil, throw in a cube or two and enjoy!