The security check at the airport Helsinki Vantaa normally goes quite fast. That leaves lots of time for a hot drink and a small snack. And the probably best place for that is Johan & Nyström. The Swedish coffee chain that also sells its coffee through other vendors runs a really nice little café here at Terminal 1.
You can find delicious hot and cold sandwiches with e.g. egg and caviar, peanutbutter and tomatoes or cheese and melon here. And of course you can get their delicious coffee as cappuccino, espresso or just black.
Enjoy and have a good flight!