Two slices of that light brittle bread slapped on with a generous spread of kaya and crushing a thick slab of buttery goodness between its loving embrace is a typical kopi tiam fair. The quality and type of the bread is particularly important to nail that old style kopi tiam feel which adds considerably to the environment to an establishment. The bread must be of the lightest weight and toasted just so that the whiteness of the bread is maintained and doesn't turn a delicate brown (although discolouration around the bread can be countenanced). The toaster (be it man or machine) should also ensure that the bread white is toasted to reach a vulnerable firmness and does not turn hard. Toasting it just right would result in the bits of the bread being brittle which then spills around your plate if not of it. It's messy but it's cool cos it's retro, you know!
And then there is the kaya itself. Though the colour of kaya is not terribly important because even if it looks like some half digested faeces, do not be surprised if it still tastes kajagoogood. However, I think kaya should be a dark, deep brown or at worst like caramel, because it looks best with that colour. I have often been inspired to polish off a bottle of kaya simply because the colour looked so attractive (and okay, okay, the damn thing was pretty good too). I find that if the colour is right, the taste usually follows suit. Slapping green kaya on your bread is just not on. Grass is green. Kaya is a sexy sensual brown. If' anybody finds a pink kaya maker please exterminate them. They are a gross affront to our culture.
As for the butter, you cannot go wrong with this. Butter is fattening and unhealthy, which means it is going to be as tasty as it is bad for us. Which is why you must cut a slice so thick you will grow man tits just after having one serving. Cos if it don't hurt, it ain't good. Using margerine or any other low fat substitute used to be punishable by death in the more ancient though civilized Persian cities though that law has since been abandoned not so much due to disuse but because the Persian cities ran out of low fat substitutes.
This snack/meal (if you eat many enough) is best eaten on Sunday morning with a teh tarik and eaten while reading the local newspaper (if you don't throw up while reading its drivel). You may eat it on Monday, but then everybody will know you are a sad pathetic bastard with no life if you did. And you don't want that. Kaya! Kaya! Haiyaaaaa!