In a food processor, blend onions, garlic, ginger, lemongrass, coriander, chilis, harissa paste and oil together until a paste forms. Add the bottom halves of the cilantro and blend until it is incorporated. Save rest of cilantro for topping later.
Heat a dutch oven or a large sauté pan over medium-low heat. Add paste and cook for 5 to 7 minutes, stirring frequently to keep the paste from burning.
Raise the heat a little and add stock, coconut milk, curry, maple syrup, kaffir lime leaves and a teaspoon or two of kosher salt. Let broth simmer, partially covered, for 20 minutes.
In a separate pot, bring 8 cups (1.8 liters) of water to boil. Be sure to add a few pinches of salt to the water. Once the water boils, add rice noodles and cook for 3 minutes. Drain noodles and rinse with cold water. If you are nearly ready to serve the laksa, divide noodles into bowls. If you are waiting at least 15 to 20 minutes before serving, keep noodles submerged in cold water to prevent them from sticking.
Slice tofu block into 6 slices, lengthwise. Chop each tofu slice into 8 cubes. Set aside.
When the soup is ready, fish out the kaffir lime leaves, if you're using them. Add salt, if necessary.
Divide noodles into bowls. Add tofu cubes and spoon soup into the bowls. Squeeze a tiny bit of lime juice over each bowl of noodles. Top with carrots, microgreens, sesame seeds, and sliced peppers, if you like.
Store leftover noodles and soup separately.