Remove the corned beef from packaging and rinse. Place in a large pot. Cover with cold water. Stud the lemon with the cloves. Add lemon to the pot along with the muslin bag of coriander seeds. Place over high heat and when boiling, reduce the heat to medium-low and simmer for one hour
Towards the end of cooking the beef, make Granny’s mustard sauce. In the top of a double boiler, mix the egg, mustard and sugar together. Slowly add the vinegar and ½ cup water from the cooking pot. Cook over low–medium heat, stirring for several minutes until thick.
Slice the beef and serve with potatoes, steamed carrots, sauce, and parsley to garnish.