Preparation

On your mark…
With a vegetable brush or paper towel, brush off any dirt from the mushrooms. Coarsely chop the mushrooms and set aside.

Peel the onion, finely chop, and set aside.

Slightly crush the garlic by laying the flat side of a chef’s knife on the clove and pressing firmly to break open the skin. Remove the skin, cut off the root end, and discard. Coarsely chop and combine with the onion and set aside.

Wash the tomatoes and cut out the stem circle at the top. Chop the tomatoes, add to a small bowl, and set aside.

If you are using fresh basil leaves, wash and shake to remove the excess water and dry by rolling in paper towels. Tear into small pieces and set aside.

Get set…
Using the largest holes of a four-sided grater, grate the fontina, mozzarella, and Parmigiano-Reggiano cheese and combine in a medium bowl. You should have a total of 150 grams (1½ cups) of grated cheese. Add the milk, mix well, and set aside.

Cook!
Preheat the oven to 204˚C (400˚F) with a rack in the middle of the oven.

Heat the olive oil in a 30 cm (12-inch) skillet over medium heat for 30 seconds until hot but not smoking.

Add the onion and garlic and sauté for 3 to 4 minutes, until translucent. If the onion starts to brown, lower the heat.

Add the chopped tomatoes, basil, oregano, salt, pepper, and butter. Cook for 3 to 4 minutes, until the tomatoes are tender.

Mix the cornstarch and 118 ml (½ cup) water and add to the tomato sauce, stirring to combine with all the ingredients.

Add the chopped mushrooms and mix all the ingredients together. Be careful not to spill the ingredients over the edge of the pan.

Add the cornstarch-water mixture and stir well. Reduce the heat to low and cook at a gentle boil for 15 minutes, or until most of the liquid has thickened. Stir occasionally to prevent sticking. If necessary, reduce the heat.

Cut the polenta into long ½-1 cm (¼ -to ½-inch) slices. Arrange them, so they cover the bottom and the sides of a 25 cm (10-inch) cast-iron skillet or baking dish. It is all right if some of the pan shows through the slices.

Spoon one-half of the tomato mixture evenly over the slices. Then spoon one-half of the cheese-and-milk over the tomato mixture.

Repeat the steps above with another layer of polenta slices, ending with the cheese-and-milk mixture on top.

Bake for 40 to 45 minutes, or until the top is browned and bubbly. Let the pie cool for 30 minutes or until the filling has set. Cut into slices and serve hot.