Clean the chanterelles with a damp cloth and trim off any dirty bits. Do not wash. Cut into thick slices.  Melt 3 tablespoons of the butter over medium heat in a 2-quart or larger heavy bottom pot and add the chanterelles.  Sauté for 5 minutes, stirring as needed and season with salt and pepper. Add 1/4 cup of the mushroom stock and cook until the chanterelles are just tender. Transfer the chanterelles to a bowl and set aside.

Heat 2 tablespoons butter in the pot over medium heat. Add the onions, garlic, 1 teaspoon salt and 1/2 teaspoon freshly ground black pepper. Cook, stirring, until the onions are translucent, about 5 minutes. Add the rice and cook, stirring, for about 2 minutes. Begin adding the stock, 1 cup at a time, waiting for the rice to absorb the stock before adding the next cup. After you've used 3 cups of stock, add the sparkling wine, then stir in the reserved chantelles.

Add in two more cups of stock in the same manner as before, allowing the rice to absorb the liquid before adding more, then add the tomatoes. At this point the risotto should be a little chewy and a bit saucy. Add more stock as needed continueing to cook until the rice is just tender.   Remove from the heat and stir in the parmesan, parsley and the softened butter.  Serve immediately.