Place the pine nuts in a skillet with a tablespoon of the olive oil and keep them moving in the pan over medium heat until they are golden but not burned. Set them aside and add the rest of the olive oil. Sauté the onion, garlic, salt, pepper, capers, olives, tomatoes, and balsamic vinegar. After the tomatoes have cooked down to a chunky sauce, add the toasted pine nuts and the cocoa powder.