In a large Saucepan (big enough to hold the leg bone) melt the butter over a medium/low heat. Add the sliced onions and sweat until softened about 7 minutes add garlic and saute for 3 minutes.
Meanwhile, cover the split peas with water and allow to soak.
Add the leg ham bone and cover with water (approx 2 1/2 - 3 liters of water), bring to a simmer and reduce heat, cooking until the ham meat falls from bone about 1 1/2 hrs.
Once the ham has cooked, remove the bone and meat and allow to cool.
Drain the split peas and then add to the saucepan, cooking until the pulses are soft around 45 mins.
Meanwhile, remove the meat from the bones and shred. Discard the bones.
When pulses are cooked add 2 cups of the baby peas and cook for 10 minutes.
Blend the soup until smooth and place back onto the heat.
Add the shredded ham (reserving some for garnish optional) and the remaining cup of baby peas and cook until ham and peas are heated through.
Serve in bowls topped with some shredded ham and finely shredded mint leaves.