Use 1 tsp of the olive oil to grease a 23cm (9 inch) square baking dish or tin.
In a large saucepan, bring the vegetable stock to the boil. Sprinkle in the polenta, stirring constantly with a whisk or wooden spoon.
Lower the heat and cook the polenta, stirring, until it becomes very thick. This will take about 5 minutes. Stir until completely cold, then cut into 4 equal pieces.
Preheat the grill. Bruch the polenta pieces with a little olive oil, then grill them for a few minutes on each side. Grill the cherry tomatoes at the same time.
Heat the remaining olive oil in a frying pan and cook the mushrooms for a few minutes on each side. Grill the cherry tomatoes at the same time.
Serve the polenta with the mushrooms and cherry tomatoes, topped with slices of Parma Ham. Accompany with some rocket leaves, if you like.