 They are cooked until halved in volume and the water is then sieved.For every 1000ml water, 500g sugar is added and the concoction is again boiled, until thread point is achieved.Quince cheese is sold in squares or blocks, then cut into thin slices and spread over toasted bread or sandwiches, plain or with cheese, often served for breakfast or as a snack, with manchego, mató, or Picón cheese (Spain) or Queijo da Serra da Estrela, Serra da Estrela cheese de Azeitão Queijo de Azeit%C3%A3o or São Jorge S%C3%A3o Jorge cheese cheeses (Portugal).