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.

While the sauce is simmering, prepare the beef. Toss the sliced beef in a small bowl with cornstarch and a sprinkling of salt and pepper. In a nonstick skillet, heat the remaining oil over medium high. Add the beef to the pan in a single layer and brown on both sides. Stir the beef into the noodles and add the bok choy and cover for 2 more minutes. In the pan you cooked the beef in, add the eggplant and brown. Add the cooked eggplant, bamboo shoots and thai basil to the pasta and stir until combined. Season to taste with salt and pepper. If the sauce is a little thick, add some more chicken stock or coconut milk at the end.