Preheat oven to 180°C/gas mark 4.
Grease an 23cm x 34cm baking sheet pan with oil. Line pan with waxed paper. The oil will secure the waxed paper onto the pan.
In a large pot bring to a boil 2 liters of salted water. Stir in extra-virgin olive oil. When water has reached a boil, reduce heat to medium high and slowly add the polenta, whisking constantly for three minutes. When polenta is thick and smooth, pour it into the prepared pan. Spread the polenta evenly.
Bake in oven for 15 to 20 minutes.
Remove from oven and allow to cool in pan.
Note: the polenta will not brown or change in color. When cool enough to handle, cut into any shape you desire. I like to cut out 4cm circles.