Reintroduce yourself when she answers the phone. Use a 10-second soundbite such as: "Hi, Clara. This is Ken. I had such a great time talking to you at our friend's birthday party the other night."
Ask her to join you in doing something that stimulates her mind, based on what you already know of her interests. If you know that she enjoys art, engage her in a few minutes of chat about her day, then mention that you have been thinking of going to an art lecture, and would love if she joined you. If she likes biking, mention that you're thinking about biking through a local park. Be subtleand genuine, rather than just another guy asking her out to dinner and drinks.
Make solid plans for a date and time to meet, if she agrees. If she declines, tell her you will call her the next time something fun comes up that she might be interested in. End the conversation on a friendly note and hang up the phone.