Heat the stock in a small saucepan, add a pinch of saffron strands and allow to infuse for 10 minutes.

Melt the butter in a medium skillet. Sauté the onion and garlic for 5 minutes over low heat or until soft.

Add the rice and stir over medium heat for 2 - 3 minutes, or until it is opaque. Pour in wine; simmer rapidly until most of the liquid has evaporated.

Add a third of the warm stock, stir once, and simmer very gently over low heat until liquid is absorbed. Repeat this process twice with the remaining stock until the rice is tender, about 25 minutes.

Just before the rice is cooked, in a small skillet, heat the oil and stir-fry the mushrooms about 4 - 5 minutes. Add arugula, stirring briefly until just wilted. Stir the mushrooms and arugula into the rice, along with the Parmesan cheese, salt, and plenty of pepper. Serve immediately.