In a baking tray add the beef bones. Bake them for 1 & 1⁄2 hours at 200 °C/ 392 ℉.
Later, remove them from the oven and spread the tomato paste.
Bake again for another 30 minutes.
In a cooking pan add the extra virgin olive oil.
Sauté the onions and the garlic cloves till caramelized and add the carrot, the leek, and the thyme.
Stir with the red wine and let the alcohol evaporate.
Add the beef bones and the water. Let cook, in slow/medium fire/ heat for 30-40 minutes.
Remove the bones from the pan. Place the liquid mixture in the blender. Blend till homogenized.
add the liquid mixture in the chinois for a milder result sauce.
Place the sauce in the cooking pan and let broil for 30 more minutes until thicken.
Remove the sauce from the heat and add the dark chocolate in the pan