Prepare the polenta according to the package directions. As soon as it is ready, pour it into a pan greased with oil, level the surface with a spoon and leave to cool.
Cut out about 5-6 cm squares of polenta and grill them on a hot grill for a few minutes on each side until crispy.
Garnish the croutons with slices of prosciutto crudo, semi-dried cherry tomatoes, fresh spinach leaves and shavings of Grana Padano.
Serve the polenta croutons warmed.