In a dutch oven heat oil on medium and begin to render/cook the lamb ribs, fat cap side down until the fat cap on each rib has reduced by half, about 20 minutes on low heat. Take your time, and if the pan threatens to dry out, add a little water or stock.
Remove ribs and pour off all fat except a few tablespoons.
Sweat the onions and garlic on low heat for a few minutes until fragrant, then add the chili’s, and lemongrass.
Add fish sauce, tumeric and sugar.
Allow sugar to dissolve, stirring occasionally.