Place oxtails and butter in a Dutch oven or large soup pot.

Add sliced carrots, turnips, onions, leek, celery, herbs, bay leaf, peppercorns, cloves, chopped ham, and 1 cup of water.

Cook over high heat, stirring occasionally, until the vegetables soften, about 8 to 10 minutes.

Add the remaining water (except for 1/2 cup) and bring to a boil.

Add salt and skim off any fat and scum that rises to the surface.

Simmer gently until the oxtails are tender, approximately 3 to 3.5 hours.

Remove the oxtails from the pot and set aside.

Skim fat and scum again from the soup.

Strain the soup, discarding the vegetables, herbs, spices, and ham. Return the strained soup to the pot.

Combine flour and 1/2 cup water to form a slurry.

Add the flour slurry to the soup to thicken it.

Add ketchup and Port wine to the soup.

Return the oxtails to the soup and simmer for an additional 5 minutes to heat through.