Remove the veins, tendons and gall bladder from the chicken livers. Dry them with paper towels. Heat the oil in a frying pan and add the livers. Sprinkle with thyme leaves, and when the liver turns white, pour the cognac over it. Very carefully, using a long match, light the cognac on fire (to burn the alcohol off, while keeping the flavour). Add the cream and simmer until thick. Remove from the heat and season to taste with salt and pepper. Serve with cooked rice.