父は私にお土産としてチョコレートをくれた。
"My dad gave me chocolate as a gift."
Can I use として in this context?
Correct.
But if the chocolate is totally appropriate as souvenir, just saying お土産にチョコレートをくれた is enough. として can carry a nuance of "as a substitute" or "as a thing that it's not intended for."
Looks correct to me. I had a look for similar examples. From http://www.linguee.com/english-japanese/search?query=%E3%81%8A%E5%9C%9F%E7%94%A3%E3%81%A8%E3%81%97%E3%81%A6
最後に全員で昼食をともにし、記念撮影を行い、Tシャツや子供たちの写真など を お土産として 配 布 し、イベントは終了しました At the end, everybody participated in lunch, there was a commemorative photo, T-shirts and personal photos of children were distributed as souvenirs - then the event came to a close.
お土産として here is used in much the same way here: (something) is given as a gift.
There are other examples there, but that was the closest to your sentence.
