For the spicy eggplant: Add 2 tablespoons of the oil to a medium saute pan over high heat. Add the red onion and sweat, stirring frequently, for about 2 minutes. Add the remaining 2 tablespoons oil, eggplant, garlic, ginger, bird's eye chile and salt. Cook, stirring frequently, until the eggplant is browned, about 5 minutes. Stir in the chicken stock, fish sauce and chili paste. Reduce the heat to medium and cook for about 15 minutes. Stir in the cilantro and Thai basil before serving.
For the fish: Add 2 tablespoons of oil to a medium saute pan over high heat. Season the fish generously on both sides with salt and lay it skin-side down in the hot pan. Sear until the skin is crispy, about 2 minutes. Flip the fish and cook for about 1 minute. Adjust the heat as needed. Transfer the fish to a baking sheet skin-side up. Bake until done, about 5 minutes.
For the red curry sauce: Pour out excess oil from the pan used to cook the fish. Over medium heat, add the scallion whites, garlic and ginger and sweat for about 1 minute. Stir in the coconut milk, chicken stock, palm sugar, fish sauce, red curry paste, kaffir lime leaves and lime zest and juice. Bring to boil, then reduce to a simmer and cook until the sauce thickens, about 15 minutes. Taste and adjust the seasoning as needed. Before serving, stir in the scallion greens.
For serving: Top the fish with the red curry sauce, peanuts, cilantro and Thai basil. Serve with the spicy eggplant.