Haven't tried this recipe, but we were served this appetizer in Montecino. It was grand! Here is one version:

Grilled Polenta with Mushrooms (Crostini di Polenta con Funghi)
Serves 4

For polenta:
4 cups water
1 cup coarse yellow cornmeal
1 teaspoon salt

For the mushrooms topping:
3 Tablespoons unsalted butter
1 Tablespoon olive oil, and more for brushing polenta
1 finely chopped garlic clove
3/4 lb fresh mushrooms, any one kind or any combination to equal 3/4 lb, halved or quartered if large
1 teaspoon chopped fresh thyme or rosemary
salt and freshly ground pepper to taste
1 tomato, chopped
1 Tablespoon chopped fresh flat leaf Italian parsley

For polenta: Bring water to a boil in large saucepan. Add cornmeal in a slow, steady stream, whisking constantly to prevent lumps from forming. Add the salt. Reduce the heat to low and cook, stirring frequently, until polenta thickens and begins to pull away from the sides of the pan, 30-40 minutes.

Meanwhile, oil a 12x9 inch pan.

When polenta is ready, pour it into the prepared pan, spreading it evenly with a spatula dipped in cold water. Let cool to room temperature until firm about 1 hour, or cover with plastic wrap, place in the refrigerator and chill overnight.

For the mushroom topping:
In a large frying pan over medium heat, melt the butter with the 1 Tablespoon olive oil. Add the garlic and cook, stirring until lightly golden, about 30 seconds. Stir in the mushrooms, thyme or rosemary, salt and pepper. Cook, stirring frequently, until the mushrooms are browned, about 10 minutes. Add the tomato and cook until juices have evaporated, about 10 minutes more. Stir in the 1 Tablespoon parsley and remove from heat. Cover and keep warm.

Preheat broiler.

Cut polenta into 8 pieces and brush on both sides with olive oil. Arrange on a heavy baking sheet.

Broil 4 inches from the heat source, turning once, until crisp and golden on both sides, about 3 minute on each side.

Place 2 polenta, (now called polenta crostini) on each plate. Top with the mushroom mixture, dividing evenly and sprinkle with parsley. Serve hot.