Position a rack in the middle of the oven and preheat to 400°F.
Heat the oil in a medium-sized saucepan over low heat. Add in the ginger, garlic and onion, cover and cook for 8 minutes, stirring halfway in between. Raise the heat to medium and add in the leeks, cumin seeds, 8 cardamom pods, red pepper flakes, curry, turmeric and cinnamon. Cook, stirring often, for 2 minutes, then add in the tomato paste, cooking for an additional 30 seconds.
Add in the wine, stock, yogurt, coconut milk, lemon juice, and ½ teaspoon salt. Bring to a boil and turn off the heat. Season with freshly ground black pepper and additional salt, if necessary.
Take the snapper and score it 3 times diagonally on either side. Season all around, as well as inside, with salt and pepper. Place the lemon slices in the fish cavity. Place in a shallow heatproof baking dish, large enough for the whole fish, and pour the curry sauce over the fish, making sure to cover the top of the fish with the leeks. Cover with foil and bake for 30-40 minutes, depending on the size of your fish (about 13 minutes per pound). Fish should be opaque and cooked through.
Serve in the baking dish or on another platter with the sauce spooned over the top. Spoon the sauce over the fish and garnish with chopped mint and cilantro. Serve immediately.