Bring the chicken stock (or water) and salt to a boil in a medium saucepan over medium-high heat. Slowly add the polenta, whisking constantly.
Continue to whisk until the mixture thickens, about 2 to 3 minutes. Turn the heat to low and cook, stirring occasionally for 20 minutes. Season with the pepper and stir in the Parmesan until fully incorporated.
Line a 9x9-inch cake pan or baking dish with parchment paper and pour the polenta in and spread in an even layer. Cover and refrigerate until it becomes firm, for at least an hour.
Cut the polenta into 9 squares. Heat a large non-stick pan over medium heat, add the olive oil and heat through. Working in batches add the polenta to the pan and fry until golden brown, about 5 minutes on each side. Remove and set aside.
For the spicy tomato sauce:
Heat a large saucepan over medium heat, add the olive oil and heat through. Add the onion and sauté until sot and opaque, about 6 minutes. Add the garlic and cook for an additional 30 seconds. Add the tomatoes and basil, stirring to combine.
Simmer until the sauce comes together, about 30 to 45 minutes, adding more water if the sauce gets too dry. Stir in the red pepper and season with salt and pepper.
For the sautéed kale:
Heat a large high-edged sauteuse pan over medium heat, add the olive oil and heat through (may have to work in two batches depending on the size of the pan). Add the kale and toss to coat in the oil. Sauté, stirring occasionally until the kale has wilted.
Lower the heat to medium-low then add the chicken stock and simmer until the kale is tender and most of the stock has evaporated, about 8 minutes.
For the mushrooms:
Heat a large sauté pan over medium heat, add the olive oil and heat through. Add butter and allow to melt, then add the mushrooms and cook, stirring occasionally, for 4 minutes. Season with salt and continue to cook until golden brown, about 4 minutes.
For serving:
Divide the crispy polenta among plates with kale and mushrooms. Top with sauce and Parmesan.