Heat the oil in a soup pot over medium heat. Add the garlic, ginger, and lemongrass; sauté for 3-5 minutes (but don’t let the garlic brown – if it starts browning, remove from heat / turn the heat down).
When everything is soft-ish and smells really nice, add the roasted red chili paste and sauté for 1-2 minutes. Add the mushrooms and red pepper (and any other veggies you like). Sauté for 3-5 minutes to get them sweating a bit, and then add the tofu and broth and bring to a simmer. Simmer for 10-15 minutes.
Add coconut milk, fish sauce, brown sugar, lime juice and zest, and salt. Stir in the cilantro. Taste and adjust till you get it just how you like it. Pull out the lemongrass chunks.
Ladle the soup over a shallow bowl filled halfway with rice – so the soup kind of goes on one side and the rice on the other, with the coconuty broth spilling over into the rice a bit. Top it off with extra cilantro and chili oil.
