Soak split peas and bicarbonate of soda in cold water overnight.
Cover ham hock with 1.5 to 2 liters of water and bring to a boil.
Drain and wash the ham hock and pan to remove starchy foam.
Return ham to the pan with fresh water, studded onion, mace, and bay leaves.
Simmer the ham for 1 hour.
Boil rinsed split peas in a separate pan for 10 minutes, then drain.
Add drained peas, diced onion, and carrot to the ham pan.
Simmer for 45 to 60 minutes until peas are tender.
Remove ham hock, whole onion, bay leaves, and mace from the liquid.
Shred ham meat into pieces, discarding skin and bone.
Add mustard, salt, and pepper to the soup and blend to a rough purée.
Return ham to soup and fold in whipped cream if using.