Bring 1 liter of water to a boil in a 3-quart saucepan over high heat. Add 1 tsp fine sea salt.

Pour in the polenta in a steady stream while whisking constantly to prevent lumps.

Reduce heat to low and cook, stirring with a wooden spoon every 2 to 3 minutes, for 25 to 30 minutes until the polenta pulls away from the sides of the pan and is thick enough to hold a channel.

Remove from heat. Stir in the butter and grated Parmesan until both are fully melted and incorporated.

Lightly oil the baking dish with a little olive oil. Pour the polenta in and smooth to an even layer about 2 cm thick. Let cool at room temperature for 20 minutes until fully set and firm enough to slice.

Heat 2 tbsp olive oil in a medium skillet over medium heat. Add the sliced garlic and cook for 1 to 2 minutes until fragrant and just starting to turn pale gold - do not let it brown.

Add the crushed tomatoes, chopped kalamata olives, dried oregano, chili flakes if using, salt, and black pepper. Stir to combine.

Simmer over medium-low heat for 5 minutes until the sauce thickens slightly. Remove from heat.

Heat the oven to 200 C / 390 F.

Once the polenta is set, use a sharp knife to cut it into 8 even rectangles or squares directly in the baking dish.

Spoon the tomato-olive sauce evenly over the top of the polenta slices, spreading it to the edges of the dish so no polenta is left dry.

Drizzle 1 tbsp olive oil over the surface. Scatter extra Parmesan on top if using.

Bake for 25 to 30 minutes until the sauce is bubbling and the exposed polenta edges are golden and slightly crisp.

Remove from the oven and rest for 5 minutes. Scatter fresh basil leaves over the top before serving.