1.Place tamarind pulp and the boiling water in a bowl; soak 15 minutes. Strain mixture through a fine sieve; discard solids.
2.Preheat oven to 160°C.
3.Heat oil in a large, non-stick frying pan over medium heat; cook ribs, in two batches, 3 minutes each side or until browned. Transfer to a large deep roasting pan.
4.Add tamarind liquid, stock, sugar, sauces, ginger, garlic and lemon grass to pan, cover with foil; roast about 2 hours. Remove foil; roast a further 1 hour or until meat is very tender and sauce is reduced.
5.Transfer ribs to a large bowl and cooking liquid to a medium bowl. Cover bowls with plastic wrap; refrigerate 4 hours or until fat has solidified.
6.Scoop off solidified fat from cooking liquid; discard. Place 2 cups of the cooking liquid in a deep frying pan (discard remaining liquid) over high heat. Add ribs; cook 10 minutes, turning occasionally or until sauce boils and reduces, and ribs have warmed through. Top with mint and chilli; serve with lime.
If Vietnamese mint is unavailable you can use spearmint leaves instead. You can serve this recipe with jasmine rice, if you like; you will need to cook 1¼ cups (250g) rice to serve six. This recipe can be prepared to the end of step 5, up to 2 days ahead.