Preheat the oven to 350ºF. Brown the ground goat meat and guanciale in a deep, ovenproof saucepan. Remove the meat from the pan and add the mirepoix. Sweat the mirepoix; then add the goat and guanciale back into the pan and deglaze with the red wine. Reduce the mixture by half and add the San Marzano tomatoes. Cover the pan and bring the mixture to a simmer. Put the pan into the preheated oven and cook for 6 hours. Remove from the oven, add the ground, uncooked chicken livers, mix, and let cool. Season with salt, pepper, and chili flakes.