This filling is enough for 2 or 3 sandwiches, depending on how stuffed you like your sandwich and you could also have this as a toast.
You can instead mash this paste with a fork or with a potato masher, just remember to finely chop the onion and the parsley and crush the garlic clove in advance.
As this is a super versatile filling, you can add any other ingredient of your likings, like other herbs or pickles, for example.