Yep, it's a pat slicer !

As in 'butter pat' slicer. Silly little thing that brings me great joy. (Found at Bed, Bath & Beyond if you must know!). Then I stagger the pats on my butter dish so they are easy to separate when needed. My friends call me the gadget queen but they laugh cuz I really use them ! Aaahhh the good life, haha.