1. Heat the oven to 200°C, 400°F, Gas Mark 6.
2. Prepare the duck breast by drying the skin with kitchen paper. Take some ground sea salt and rub it onto skin.
3. Put the duck breasts on to a cold dry sauté pan skin side down and turn the heat to medium. Cook until the skin is brown and crispy, about 7 minutes.
4. Remove the duck breast from the pan and place skin side up in a roasting tray. Roast until done to your liking. Usually about 12 minutes for medium rare but it all depends on the thickness of the duck breast. Remove and allow the duck breast to rest.
5. From the tin of coconut milk, scoop out the solid part if possible and place in a wok or pan. Add the Thai paste and cook gently for 3-4 minutes. Add the palm sugar and fish sauce and the rest of the coconut milk. Simmer for a further 2-3 minutes. If you like more sauce add a little water, chicken or vegetable stock
6. Add the tomatoes and choy sum or bok choy and cook until tender, 3-4 minutes.
7. Slice the duck and add to the curry, mix well. Add the lime juice, sliced spring onions and the chopped basil. Garnish with chopped chilli if desired.
Serve with Jasmine rice.