In a large pot, prepare the vegetable broth by adding the vegetable bouillon, the fresh thyme, and the bay leaf to the water. Bring to boil, and keep to a high temperature throughout the cooking of the risotto.
Make the balsamic vinegar glaze
In a small pot, add the balsamic vinegar and let reduce on low heat for about 10 to 12 minutes.
Set aside and let cool down. At this point the balsamic vinegar should have thickened and should be pourable with a spoon.
Make the pumpkin purée
Peel, seed, and cut the pumpkin into small dice. Then cook it in a pan with one glass of vegetable stock until soft.
With a hand blender, turn the pumpkin into a smooth purée. Season with salt and pepper and set aside.
Cook the risotto
In a pan on medium heat, toast the risotto rice for about 2 minutes (do not add oil, onion, butter, or water). Stir frequently.
Add a splash of water to the rice to lower the temperature of the pan.
Add the hot vegetable broth, one ladle at a time, and keep stirring.
Repeat this until the risotto is cooked.
Take away from the heat and add the pumpkin purée to the risotto. Fold in gently. Keep the risotto moist, if necessary add more vegetable broth.
Fold in the nutritional yeast, and season with salt and pepper to taste.
Serve with crush walnuts on top, a drizzle of balsamic vinegar glaze and some fresh thyme.