Pre-heat a large Dutch oven over medium-high heat.

Add the butter to the pot and then add the onion, celery, carrots and garlic. Cook until the vegetables just begin to soften. Add the fresh thyme, split peas, ham bone and 6 cups of the water and cover.

Bring to a boil, reduce the heat and simmer for about 40 minutes, or until the split peas and vegetables are soft. As the soup simmers, if it starts to get a little too thick, add more water.

Remove the ham hock from the pot and let it cool enough to pull any meat from the bone. Set the meat aside.

Meanwhile, using a blender, or an immersion blender purée the soup and return it to the Dutch oven. Season to taste with salt and pepper and a little lemon juice, and thin the soup with a little water if necessary. Return the meat from the ham bone to the pot, along with the cooked ham.

Serve with some crusty bread and a green salad.