In a large non-reactive pot, heat 1 cup of water, salt, sugar, and spices and whisk together until the salt and sugar have dissolved.
Turn off the heat and add the remaining water. Place the brisket in a large plastic brine bag. If using a bowl, weigh down the meat with a plate so that it is completely submerged.
Place in the refrigerator to brine for 3 weeks.
After 3 weeks remove the brisket from the brine and rinse well. Discard the brine. The elk is now corned and ready to be cooked.
Place in a large pot and barely cover with water. Add the onions and bring to a boil, then reduce heat to medium, cover pot, and simmer for 2 ½ hours, or until meat is tender. To serve, slice the meat across the grain. Serve with homemade sauerkraut and homemade mustard.