Peel the sweet potatoes and cut into 1.5cm cubes. Heat 1 1/2 tablespoons of oil. Add the sweet potatoes and fry on medium heat for 5-8 minutes until golden brown.
Finely chop the onion and garlic. Braise in the remaining oil together with the risotto rice. Gradually pour in the hot vegetable stock. Allow to simmer for 20 minutes and stir occasionally.
Cut around half the Gruyère AOP into slivers and finely grate the rest of the cheese. Finely chop the rosemary.
Mix the sweet potatoes, rosemary, cranberries, and spinach into the risotto. As soon as the spinach folds together, mix in the grated Gruyère AOP, season with salt and pepper and cover with the Gruyère AOP slivers.