For the Manchego and sage polenta, place the polenta into a saucepan with the stock. Bring to the boil and simmer for 1-2 minutes.
Stir in the grated Manchego, butter and sage. Season with salt and freshly ground black pepper and add a little water if the mixture is too thick.
For the nut-brown sage butter, heat the butter in a small saucepan until it turns a nut-brown colour, taking care not to burn it. Add the sage leaves and cook for 3-4 minutes.
To serve, spoon the polenta into a bowl and pour over the sage leaves and nut-brown butter.