1 teaspoon cream of tartar
1/2 teaspoon fine salt
8 large egg whites, at room temperature
4 1/2 cups confectioners' sugar, sifted, plus more for dusting
1/4 cup black sanding sugar, plus more if needed
1 1/2 cups whole milk
2 teaspoons pure vanilla extract
1/4 teaspoon fine salt
1/3 cup granulated sugar
5 large egg yolks, at room temperature
1/2 cup heavy cream, chilled
For the meringue: Position oven racks in the upper and lower thirds of the oven and preheat to 200 degrees F.
Beat the cream of tartar, salt and egg whites in a very clean, dry bowl of a stand mixer on medium speed until foamy. Increase the speed to medium high and beat until thick and opaque, about 1 minute more. Gradually add the confectioners' sugar about 1/4 cup at a time and beat until shiny stiff peaks form, 5 to 10 additional minutes.
Invert a large baking sheet and top it with a large piece of parchment. Spoon leveled 1/3-cup portions of meringue onto the parchment, leaving ample space between each portion. Use a small offset spatula to smooth each portion of meringue into a 5-inch round.
Use a 3-tablespoon ice cream scoop to scoop 4 leveled mounds of meringue around the perimeter of each 5-inch round. Use the offset spatula to lightly smooth out the mounds so they touch each other and mimic the look of snow drifts. If needed, use the back of a spoon to create a large divot in the center of the meringue so there is enough room to pour in the creme anglaise later.
Fit a large pastry bag with a 1/4-inch round tip and scoop the remaining meringue into the bag.
Invert a second large baking sheet and top it with a piece of parchment. Spread out half of the black sanding sugar onto one corner of the parchment. Pipe one 2 1/2-inch-long by 1 1/2-inch-wide teardrop-shaped mound of meringue for the black swan's body, two 2-inch-long by 1-inch-wide teardrop-shaped mounds for the black swan's wings and one 3-inch S-shaped swan neck with head directly onto the black sanding sugar. Use a wooden toothpick to pull out the top of the head to create a beak. Sprinkle the meringue pieces with the remaining black sanding sugar. Use a pastry brush to brush away the excess sanding sugar, but reserve to use later.
On the remainder of the parchment, pipe five 2 1/2-inch-long by 1 1/2-inch-wide teardrop-shaped mounds of meringue for the white swans' bodies, ten 2-inch-long by 1-inch-wide teardrop-shaped mounds for the white swans' wings and eight 3-inch S-shaped swan necks with heads (you will have extra heads/necks, in case of breakage). Again, use a wooden toothpick to pull out the top of each head to create a beak. These do not spread much while baking, but leave at least 1/4 inch of space between each piece of meringue.
Bake both baking sheets of meringue until dry and crisp, 3 to 4 hours. Cool completely on the baking sheets.
For the creme anglaise: Whisk together the milk, vanilla and salt in a medium saucepan and bring to a simmer over medium heat, 3 to 5 minutes. Reduce the heat to low.
Whisk together the granulated sugar and egg yolks in a medium bowl until well combined, then whisk in 1/2 cup of the hot milk mixture. Slowly whisk in the remaining hot milk, then pour the mixture back into the saucepan and continue cooking at a slow simmer, whisking constantly, until the custard thickens to the consistency of thin gravy, 8 to 10 minutes. Strain the sauce into a medium bowl and cover with plastic wrap. Refrigerate until completely chilled.
For the whipped cream: Put the heavy cream in a medium bowl and whisk vigorously to stiff peaks.
To assemble: Use a small offset spatula to gently loosen the meringue pieces from the parchment. Transfer the 6 lakes onto individual plates. Spoon 2 leveled tablespoons of the whipped cream onto each swan base. Gently insert a swan head/neck toward the tip of each base, then press 1 set of wings onto the sides of the whipped cream. Repeat this process to build 5 additional meringue swans. There should be 5 white swans and 1 black swan. For the black swan, sprinkle a thick layer of the excess black sanding sugar all over the whipped cream before inserting the head/neck and wings.
Pour the chilled creme anglaise into the center of each lake, then top each with a swan. Dust with confectioners' sugar and serve immediately.
The meringues can be baked up to 1 day in advance (avoid baking in humid weather); keep them overnight in the oven with the oven turned off. The crème anglaise can be made up to 2 days in advance and kept refrigerated. Whip the cream and assemble the swans just before serving.
Some people find it easier to trace the shapes of the meringues onto parchment first with a pen to use as a guide; flip the parchment over before piping out the meringue.