Mushroom risotto with caramelized onions

Heat the oven to 150°C/300°F/gas 2. Rinse the dried mushrooms lightly, to remove any dust or grit. Place the mushrooms in a ceramic bowl and pour the boiling water over them. Set them aside to steep while you cook the onions. Finely dice the onions. Heat 2 tbsp of olive oil in a large sauté pan over medium heat. Add the onion and garlic and cook, stirring occasionally, for about 8 minutes, or until soft and golden. Push the onions to the side of the pot, and turn the heat up to medium-high. Add all the sliced cremini mushrooms and let them cook for 5 minutes without stirring. Flip the mushrooms and cook for another five minutes, or until they are brown. Drain the dried mushrooms, reserving the liquid.Add the mushrooms and rosemary sprig to the pan and sauté briefly, mixing with the onion and the rest of the mushrooms. Add the rice and cook, stirring once or twice, for about 4 minutes, or until the rice begins to turn translucent. Turn the heat to high and add the white wine, vinegar, broth, and reserved mushroom steeping liquid. Stir in the salt and pepper. Bring to a boil. Cover the pan with a tight-fitting lid and put it in the oven to bake for 35 minutes.While the rice is baking, makethe caramelized onions. Heat the remaining olive oil in a non-stick skillet. Cut the remaining three onions in half, and thinly slice them. Add them to the oil and sprinkle liberally with salt. Cook on low heat, stirring occasionally, until the onions turn a dark brown (about 20 minutes).