Preheat the oven to 450˚F. Line a small baking sheet with foil or parchment paper.
In a small saucepan, bring the stock, porcini, and 1 cup water to a simmer over medium-low heat. Simmer until the porcini soften and the stock is infused with flavor from the mushrooms, about 5 minutes.
Pull the hen-of-the-woods mushrooms into thin florets and place on the baking sheet. Spray the mushrooms with cooking spray until evenly coated. Season with salt and pepper. Roast, tossing once, until crispy and browned, 20 to 25 minutes.
In a round-bottomed saucepan or pot, heat the oil, two turns of the pan, over medium. Add the shallot and garlic. Cook, stirring often, until softened, a minute or two. Add the rice and stir for another minute; season. Stir in the allspice. Add the vermouth and stir vigorously with a wooden spoon until the liquid is absorbed, about 2 minutes.
Begin adding the warm porcini stock, a few ladles at a time, leaving the porcini in the saucepan. Stir vigorously with each addition of stock. When the liquid is fully absorbed, add more stock. When the porcini are plump, transfer to a cutting board using a slotted spoon. Coarsely chop the porcini and add them to the risotto. (From the first addition of the stock, it will take 18 minutes for the risotto to cook until al dente.) Leave the last few spoonfuls of stock in the pan since this is where the grit from the mushrooms will settle. During the last 5 minutes of cooking, add the kale. During the last minute of cooking, melt the butter into the risotto and then melt in the cheese; season. Serve the risotto in shallow bowls and top with the roasted hen-of-the-woods mushrooms.