Dear _______:

I hope this letter finds you in good health and high spirits. I was delighted to receive your birthday present, and I wanted to take a moment to express my sincere gratitude.
Your thoughtfulness and generosity have deeply touched my heart. Your gift is not only a reflection of our friendship, but it also reveals that you know my tastes and interests very well. I was thrilled to unwrap the package and find ____________ inside/outside. It was just perfect! I truly appreciate your efforts to make my birthday special.
In today's fast-paced world, it is not often that we take the time to express our gratitude and appreciation for the wonderful things that happen in our lives. I feel so lucky to have you in my life as a friend. Your presence has brought me immense happiness, and I could not have asked for a better partner in crime. Thank you for always being my confidant, my sounding board, and my ally.
I hope that you truly understand how much your gesture means to me, and that I am truly grateful to have received such a wonderful birthday gift from someone as kind and thoughtful as you. The next time we meet, we should celebrate our friendship and the amazing bond that we share.
Once again, I express my heartfelt thanks for your lovely present, and I look forward to catching up with you in person soon.
With gratitude and love,
[Your Name]