Heat up a Dutch oven or saucepan over a medium flame. Sear the sausages in peanut oil on all sides. Remove the sausage from the pan and place them in the chicken stock. Degrease the pan.
Add the butter and bay leaves to the degreased pan. When the butter is melted, throw in the onions and a little salt. Sweat the onions down until the onions are clear. Add the Arborio rice, stir the mixture until the grains are semi-toasted.
Pour in the pre-heated wine and stir. Allow the wine to reduce to almost dry. Pour in a ladle or 2 of preheated stock (about 1/2 cup), to barely cover the rice. From this point on, stir almost constantly until rice is cooked. Adjust the heat so that the liquids remain just above simmering. Keep a close eye on the rice. Add the stock when the liquid reduces by two thirds. Repeat this stock addition until the rice becomes creamy and al dente (about 20 minutes). Season the rice with salt, pepper, cayenne pepper and nutmeg. Stir in the mustard. Cut off the heat. Cover the pan, and allow to rest 3-5 minutes.
Ladle the mustard risotto onto a serving platter. Serve the Bratwurst over the risotto.