I remember seeing cubes that have solid inside that has melting point around (good temperature to drink coffee). You put them in a cup and it 1. Quickly cools

I remember seeing cubes that have solid inside that has melting point around (good temperature to drink coffee). You put them in a cup and it 1. Quickly cools coffee to that temperature (by increasing temperature and melting). 2. Keeps coffee at that temperature for some point (doesn't go lower until liquid inside is back solid). I've gave it a cursory google and can't find a name.