Wash and slice up the tomatoes into rather thick slices ( 1/2 cm ). Layer them into a fire resistant dish. If the stck it doesn't matter. Dice up the unions and fry them off in a bit of olive oil until soft and slightly coloured. Then add the garlic ( pressed, diced or even from a jar ) and fry that for 1 minute along with the unions. Once that's done, spoon it on top of the tomatoes. Clean the chicken breasts and fry or grill them until done, this should take about 15-20 minutes. When they are ready place the chicken breasts on top of the unions, seasoning with salt and pepper. (* you could add black olives, fresh basil or oregano at this step). Slice up the mozzarella and layer that on top of the chicken. Place the whole dish in a pre-heated oven (175 Celcius, electric oven ) for about 15-20 minutes.
While the chicken is in the oven cook the pasta a said on te package.
Remove the stalks from the basil and give them a wash. Grate the peccorino/parma cheese, peel the garlic. Throw everything into a high bowl and add the pinenuts and the oil. Puree/mix everything until you have a smooth consistency. Taste it and add salt, pepper or any other ingredient to your liking.
Drain the pasta and throw it back into the pan ( dont wash it with colt water just drain). Add 2 spoons of pesto each time to the warm pasta and mix. Keep on doing that until everything is mixed up pretty well and you have no pesto left. And then it's time to plate up and dig in!