Preheat the oven to 350°F and grease an 8×12 or 9×13 casserole dish.

In a very large skillet, heat 2 tbsp of the olive oil over medium heat. Add the onions, mushrooms, 1/2 teaspoon salt, and several pinches of fresh pepper, and let the mushrooms cook until they begin to soften, 5 to 8 minutes, stirring only occasionally. Add the garlic, celery, sage, and rosemary, and cook until everything is soft and the mushrooms are golden brown, 8-10 minutes.

Add the balsamic vinegar, stir, and scrape any bits off the bottom of the pan. Add the bread and the remaining 1/4 cup olive oil and toss to coat. Add the kale and cook until it begins to wilt, about 1 minute. Add 1 cup of the broth and stir.

Transfer to a casserole dish and pour the remaining 1 cup broth evenly over the stuffing.

Sprinkle with the dried cranberries, remaining whole sage leaves and bake for 20 minutes or until golden brown. Let sit for at least 15 minutes or until ready to serve.