I checked several ASL dictionaries that I found when I searched ask.com for 'ASL dictionary" and yogurt seems hard to find. I'd try to fingerspell it. here is a link to one site, it uses quicktime to run video of someone signing, but it doesn't have a search box, it only has video of the signs it lists. I found plate, spoon, fork and phone, but just apple, not applesauce, and no yogurt.
http://commtechlab.msu.edu/sites/aslweb/browser.htm
I didn't have quicktime, so I went to www.quicktime.com and it's free to download there. I wanted to see if the videos were any good, and I understood them just fine.
Good luck.