Place 2 tablespoons butter in a stainless steel bowl. Cut the remaining 6 tablespoons butter into small pieces and refrigerate. In a heavy saucepan, whisk together the milk, egg yolks, granulated sugar, cornstarch, vanilla and 1/8 teaspoon salt and cook over medium-high heat, whisking constantly, until the mixture becomes very thick and begins to boil. Place a sieve over the bowl of butter and press the custard through the sieve. Stir to incorporate. Cover the mixture with waxed paper pressed directly on the surface; refrigerate.
Preheat the oven to 425 degrees . In a heavy, 4-quart saucepan, bring 1 cup water, the reserved chilled butter, the nutmeg and remaining 1/8 teaspoon salt to a boil over high heat. Remove from the heat, add the flour all at once and, using a wooden spoon, stir to combine. Return to medium-high heat and stir the mixture constantly until dry and a smooth ball forms, about 3 minutes. Transfer to a food processor and mix for 1 minute. Add the whole eggs 1 at a time, mixing for 30 seconds between each addition.
Using a 9-inch cake pan as a guide, trace a circle onto a sheet of parchment; invert the parchment onto a baking sheet. Using a soup spoon, place dollops of the batter along the circle to make a ring. Smooth the top of the ring, joining the dollops together. Bake for 15 minutes, lower the heat to 375 degrees and bake until puffed and deep golden, about 30 minutes. Transfer the ring on its parchment onto a rack to cool completely.
Meanwhile, whip the cream until stiff. Fold half of the whipped cream into the custard, then fold in the remaining whipped cream.
Using a serrated knife and sawing parallel to the work surface, slice off the top third of the ring. Place the bottom on a platter; pull out and discard any excess dough from inside and fill the ring with the custard-whipped cream mixture. Set the top of the ring in place and dust with the confectioners sugar. Serve with the berries.