That's a failed poached egg on top, if anyone is curious.
Mentaiko is the marinated roe of pollock and is commonly used in Japanese cuisine. It's salty, a little spicy and tastes kinda seafood-ish. The flavour can be quite robust, so a little goes a long way. Here's another picture.
I still have 2 sacs of mentaiko in the freezer, so maybe mentaiko toast with... pumpkin soup tomorrow?
