PREPARE THE DUMPLINGS In a saucepan, melt 2 tablespoons of the butter. Stir in the flour over low heat to form a paste, then slowly whisk in the milk until smooth. Simmer, whisking often, until thickened, 7 minutes. Season lightly with salt; transfer the panade to a bowl, press plastic wrap directly onto the surface and let cool to room temperature.
In a food processor, puree the fish to a paste. Add the egg white and process until blended and very smooth. Refrigerate the fish paste in the processor bowl until thoroughly chilled, about 20 minutes.
Add the panade to the fish paste and process until blended. With the machine on, alternately add the eggs and the remaining 4 tablespoons of butter, scraping down the bowl after each addition. Transfer the mixture to a stainless steel bowl and stir in the white pepper, nutmeg and 1¼ teaspoons of salt. Refrigerate the dumpling mixture until thoroughly chilled, about 30 minutes.
Bring a large, wide pot of salted water to a boil. Line a large baking sheet with parchment paper. Using a 1/3 cup measure or ice cream scoop, gently shape the mixture into 8 round dumplings. Set the dumplings on the parchment and refrigerate for 5 minutes. Set a large bowl of ice water near the stove.
Lower the parchment with the dumplings into the boiling water; discard the paper. Simmer the dumplings over moderate heat, turning once, until firm, 12 minutes. Using a slotted spoon, transfer the dumplings to the ice water and let cool for 10 minutes. Drain the dumplings and pat dry with paper towels.
PREPARE THE SAFFRON SAUCE AND CHARD In a saucepan, heat the oil. Add the garlic and cook over moderate heat until golden brown, 1 minute. Add the wine and crumble in the saffron. Simmer over moderate heat until the wine had reduced by one-third, 3 minutes. Add the fish stock and boil over high heat until reduced to ½ cup, 15 minutes. Add the cream and simmer over low heat until reduced to 2 cups, 10 minutes. Add the lemon juice; season with salt and pepper.
Preheat the oven to 375°. Lightly butter a 9-by-13-inch baking dish. In a large pot of boiling salted water, cook the chard stems until tender, 4 minutes. Using a slotted spoon, transfer the stems to paper towels to dry, then arrange in the prepared dish. Arrange the dumplings on top. Pour the saffron sauce over the dumplings and bake for 20 minutes.
Meanwhile, add the chard leaves to the boiling water and cook until bright green and just tender, 2 minutes. Drain and squeeze out any excess water. Cut the leaves into small pieces. Sprinkle the dumplings with the chard leaves and baste with the sauce. Bake for about 20 minutes, until the dumplings are nicely glazed. Sprinkle with the chives and serve.