Simply replace the unfilled areas such as "" and "[date]" with your information.
Dear [name of date]
I had such a wonderful time [when date occurred, ie "last night", "Saturday"]. I enjoyed [name of activity included in date] and thought it was great that we both [name something you had in common]. I look forward to being able to get to know you better over future dates. I feel like we have a lot in common, and look forward to being able to share all the likes, and even some of the dislikes, with you.
Thank you for such a great time, and I hope to hear from you soon!