Step 1

Heat the oil in a large pot or Dutch oven over medium heat. Add the shallots and cook, stirring often, until browned, 4 to 5 minutes. Add the red curry paste and cook, stirring continuously, until the paste darkens and sticks to the bottom of the pot, 2 to 3 minutes. Add the curry powder on top of the paste and stir for 20 to 30 seconds to toast, being careful not to burn the spices.

Step 2

Add the sugar, eggplant, sweet potato, lemongrass knot, 1 1/2 teaspoons salt and 3 cups water. Stir to combine, scraping the bottom of the pot. Bring to a simmer and cover, adjusting the heat as needed to maintain a simmer, and cook until the vegetables are just tender, 8 to 10 minutes.

Step 3

Discard the lemongrass knot and add the coconut milk, string beans and tofu puffs. Simmer gently, uncovered, until the string beans are crisp-tender and the puffs are heated through, about 3 minutes. Taste and add more salt and sugar if needed.

Step 4

Serve with rice and lime wedges on the side.