Toasted Cheese Sandwich with Cumin Seeds

I had some trepidation making this - mixing dijon mustard with butter, cumin seeds, and grated gruyere. I'm not a fan of mustards with horse radish, and our dijon made my eyes tear up. However, once this concoction was broiled onto the toast (open face) it was totally transformed. The ingredient became something extraordinary. This recipe suggests serving on finger-sized slices, but I could also see eating a whole sandwich of it myself!