To prepare the fava bean risotto start heating half the butter in a large shallow pan and cook the onion and garlic over a low heat until softened and transparent.
Add the rice and stir to coat all the grains. Increase the heat and add the wine. Cook until absorbed.
Gradually add the stock, a ladleful at a time, stirring until absorbed, before adding more stock. Continue cooking until the rice is tender, but still has a little bite. Season to taste with salt and pepper.
Stir in the fava beans and remaining butter. Put the fava bean risotto into warm serving bowls and garnish with parmesan shavings and mint.