Preheat oven to 375°F. Spray a 2-quart (8x8-inch) baking dish with non-stick cooking spray and set aside.

Bring water and salt to a simmer in a large pot. Gradually whisk in the polenta. Lower the heat and cook gently, stirring every few minutes, until thick and creamy — about 30 minutes. Once the polenta is thick and pulls away from the pot, it’s ready to use. Stir in butter and remove from heat.

While the polenta cooks, heat butter and olive oil in a large skillet over medium heat. Add spinach and cook for 2 minutes, until wilted. Add garlic, salt, and black pepper. Cook for an additional 30 seconds. Stir in lemon juice, then remove from heat.

In a large bowl, combine ricotta, cheddar, fontina, mozzarella, and Parmesan cheeses.

Stir in the cooked spinach. Adjust seasoning to taste.

Spread half of the polenta evenly into the prepared baking dish. Add the spinach-cheese mixture to cover the polenta. Spread the remaining polenta over the spinach-cheese layer. Sprinkle the remaining mozzarella and Fontina cheeses over the top.

Bake in the preheated oven for 25 minutes, until golden and bubbling. After baking, let the casserole stand for 20 minutes, allowing the polenta to firm up slightly.

Sprinkle with chopped parsley and serve warm.