In a large dutch oven or pot, heat 1 tablespoon of neutral oil over medium heat. Add the curry paste, ginger and lemongrass and cook for 2-3 minutes while stirring, until the curry paste is fragrant. Add 3 cups of the chicken broth and bring to a simmer. Stir so that all of the curry paste is dissolved and there are no lumps. Add coconut milk, palm sugar (or brown sugar) and kaffir lime leaves. Stir until the palm sugar has dissolved and reduce the heat to low. Simmer for 15 minutes uncovered. After 15 minutes, use a slotted spoon to remove the ginger, lemongrass and lime leaves and discard. Add onions, peppers and noodles, stir and cover for 8 minutes.