In large saucepan, heat oil and add finely chopped onion and garlic. Sauté for 5 minutes until onion becomes transparent. Do not brown. Add salt, water, pepper, and chicken stock; bring to boil. Add instant polenta slowly, stirring for 8 minutes until smooth and slightly hard. Stir in the cheese and quickly pour the polenta into an 8- or 9-inch square oiled or non-stick pan. Smooth with spatula, cover and place in refrigerator to cool for 2 to 3 hours.
Heat grill to medium high. Slide polenta from pan to cook directly on grid. Grill 6 minutes on each side until crisp. Serve and enjoy.