Remove the skins from the sweet potato for a smoother brighter curry, and then cut the sweet potatoes into 1-inch (2.5 cm) cubes.

Steam or boil the sweet potatoes for 8-10 minutes until fork-tender. 

Drain and cool the sweet potatoes, and then blend until smooth in batches along with 8 cups of water. Set the blended sweet potato liquid aside.

Preheat the oven to 350. Cut the youtaio into 3-inch (7.5 cm) sections and roast them for 7-8 minutes to crisp them.

Blend the bird’s eye chili, curry powder, shallot, garlic, galangal, ginger, and 3 tablespoons of water for 60-90 seconds on high speed until a paste is formed.

Remove any dry external leaves from the lemon grass, cut it in half and then bruise the lemongrass by pressing down firmly on it with the side of a heavy knife or cleaver.

Heat the oil in a large frying pan, dutch oven or wok over medium heat. Once the oil is hot, add the contents of the blender and the bruised lemongrass stalk. Cook the curry paste for 3-4 minutes until aromatic and darkened.

Add sweet potato puree and the bean paste, coconut sugar, tomato paste, rice vinegar, salt, and vegan oyster sauce. Turn the heat up to high and cook the broth until it has boiled and thickened a little. If you desire a thicker curry, lower the flame after it has come to a boil, m and cook the curry without a lid for an additional 20 minutes until it has reduced to your desired thickness.

While the broth cooks, bring a pot of water up to a boil. Blanch the mung bean sprouts for 90 seconds and then remove them with a spider or slotted spoon. Set aside.

Using the same cooking water, boil the noodles according to the package instructions, then drain and rinse with warm running water to remove additional starch.

Divide the broth evenly into 4 large bowls. Using tongs, place a generous heap of noodles on one side of each bowl, and divide the bean sprouts into the other side of each bowl. Place 4-6 tofu puffs into each bowl, along with 2 sections of toasted youtiao. Garnish each bowl with jalapeños and/or sliced bird’s eye chilies, fried shallots, cilantro leaves, thinly sliced scallions, and either calamansi or lime wedges.