Division of labour

I'm sure this type of situation exists in many houses; one partner cooks an evening meal and the other one washes up.

This normally works well but there are occasions when I wonder which rule should apply.

If I cook eight meals in one go, we eat one and seven are frozen, should Dave do the washing up every time we eat any one of the eight. What if I cooked it originally but Dave got it out of the freezer and put it in the oven? What if I cooked it originally and later took it out of the freezer but Dave put it in the oven? What if....you get the gist. What should the basis be for determining who washes up?

And what should happen if we both cook our own food. An example would be if we both cooked our own omelettes. We use the same utensils and pan - who washes them?

We don't have a household rule that covers these scenarios which probably means the person that does the washing up ends up resenting the situation.

I guess the question is "What is fair?"