This dessert aptly named Raspberry Floating Island, inspired by the French "ile flottante," is an elegant way to end any meal.
Make the raspberry puree: Place 1 half-pint raspberries in a small skillet over medium heat; add 2 tablespoons sugar. Cook, stirring occasionally, until sugar is dissolved and raspberries start to break down, about 2 minutes. Remove from heat. Pass through a fine sieve into a small bowl, pressing down to extract as much pulp as possible. Set puree aside to cool.
In a high-sided 10-inch skillet, bring milk to a boil. Reduce heat to a gentle simmer while you make the meringue.
Make the meringue: In the heat-proof bowl of an electric mixer, combine remaining 3/4 cup granulated sugar with egg whites and cream of tartar. Place over a pan of simmering water; whisk constantly until sugar is dissolved and mixture is warm to the touch, 1 to 2 minutes.
Transfer bowl to the mixer fitted with the whisk attachment. Beat on low speed, gradually increasing to high speed until glossy peaks form, 5 to 7 minutes. Add vanilla, and mix to combine. Transfer meringue to a large bowl, and spread out with a large spoon or spatula. Drizzle 1 to 2 tablespoons raspberry puree on top; run a knife back and forth to streak.
Make the floating islands: Using two soup spoons, scoop and slide about 1/4 cup of meringue into simmering milk. Do not overcrowd; you will need to make these in three batches. Poach until firm, about 2 minutes per side. Remove with a slotted spoon, and transfer to paper towels to drain. Repeat, skimming surface skin from milk between batches.
Divide creme anglaise among six soup bowls. Place two meringue islands on top of each. Garnish with remaining half-pint raspberries, raspberry puree, and a dusting of confectioners' sugar.
Since raspberry seeds are small enough to pass through the finest mesh strainer, you may need to strain the puree several times.