Parboil the sausages for about 5 minutes in a pot of boiling water. Drain.
Place a large pan on medium-high heat. Coat the bottom of the pan lightly with canola oil. Tear off rosemary needles roughly and toss into pan. Add sausages and pan-grill until browned on all sides, turning as needed. By the time the sausages are ready, the risotto will be ready.
To make the risotto:
Wash and cut the potatoes into small cubes. No need to peel. Put potatoes in a saucepan, and cover with water. Add a sprinkle of salt. Bring to a boil over high heat, turn heat down and simmer about 5 min until al dente. Drain.
Heat the oil in a heavy, medium-sized saucepan over medium heat. Add the minced shallot, drained potatoes, with a pinch salt, and one ladleful of stock. Cook, stirring continuously, until the stock is almost fully absorbed.
In a separate pan, saute the mushrooms in a bit of olive oil and toss gently until they begin to brown.
Continue to add the stock to the potato mixture, one ladleful at a time, or until the potato is tender and creamy on the outside, about 5 to 10 minutes. Test it. If it's too soft, you won't need to add any more liquid. If it's still got a bite in the middle, you can add a bit more stock.
Add the mushrooms, and cheese, and stir. Add the butter, and continue stirring, adding a bit more stock if needed. Begin to 'press down' into the risotto with your spoonula so that some of the potatoes get mushed which will help to build that 'creamy' texture. Finally, add a handful of washed baby greens (arugula or baby spinach) and stir until just wilted. Season with salt, and pepper, to taste.
Place a spoonful of risotto on a warm plate and top with a single large juicy lamb sausage.
Unlike the traditional risotto, the stock can be warm or cold, it won't matter.