2 T. vegetable oil
1 T. garlic, chopped coarsely
1 c. onion or shallots, sliced
2 stalks fresh lemongrass, trimmed and cut into 2 in. lengths (optional)
5 slices fresh ginger
3 T. curry powder
1 1/2 lb. sliced chicken, cut in bite-size chunks
2 T. fish sauce
1 tsp. sugar
1/2 tsp. salt
1 tsp. dried red chili flakes
2 3/4 c. chicken broth or water
1 1/2 c. coconut milk (1 14-oz. can)
2 1/2 c. sweet potatoes or carrots, cut in chunks
2 T. lime juice
In a large deep saucepan or dutch oven, heat the oil over medium-high heat for 1 minute. Add the garlic, onion, lemongrass and ginger and toss well. Add the curry powder and cook, tossing often, until the herbs are fragrant and the onion is translucent, 1-2 minutes.
Add the chicken, spreading it out in one layer if you can, and cook for 1 minute. Toss well, and cook until the chicken changes color and begins to brown. Add the fish sauce, sugar, salt and chili flakes and toss again. Add the broth and bring to a boil. Reduce the heat to maintain a lively simmer, and cook for 10 minutes, stirring now and then.
Add the coconut milk and sweet potatoes and simmer until the sweet potatoes are tender and the chicken is cooked, 10-15 minutes. Remove the lemongrass chunks, stir in the lime juice, and then transfer the chicken and sauce to a serving bowl, and serve hot or warm.