Instructions

1. Make the crème anglaise: Place a fine-mesh strainer over a medium bowl, then place the medium bowl in a large bowl of ice water. To a medium pot over medium heat, add the milk and vanilla bean and bring just to a simmer. In a second medium bowl, whisk together the sugar, cornstarch, and egg yolks. Turn the heat to low and slowly whisk ½ cup of the hot milk into the egg yolk mixture, then whisk the egg yolk mixture into the remaining hot milk. Cook, stirring and scraping the bottom and sides of the pot continuously with a silicone spatula, until the custard has thickened enough to coat the spatula, about 15 minutes. 
2. Moving quickly, immediately strain the custard into the cold medium bowl to stop the cooking. Scrape in the seeds from the vanilla bean pods, discarding the pods, and stir in the cream. Set aside to cool to room temperature, about 10 minutes, then remove the custard bowl from the ice bath and refrigerate while you make the meringues. (This step can be done ahead of time; stored in an airtight container in the fridge, crème anglaise will keep for up to 3 days.)
3. Make the poached meringues: To a medium pot, add the milk, ½ cup of the sugar, and 8 cups of water and bring to a boil. Turn the heat to medium-low and simmer, stirring occasionally, until the sugar has dissolved, about 2 minutes. Turn the heat to low and keep warm.
4. To a large bowl, add the cream of tartar and egg whites. Using a hand mixer, beat on medium-high until soft peaks form, about 3 minutes. With the mixer still running, add ¼ cup of sugar and beat until incorporated, then gradually sprinkle in the remaining ¾ cup of sugar and continue beating until stiff peaks form, about 3 minutes more. Using a ½-cup measuring cup or a large spoon and working in batches, scoop the meringue into half-spheres or quenelles and drop into the simmering milk mixture. Cook the meringues, turning occasionally, until firm on the outside, 3–4 minutes. Using a slotted spoon, remove the meringues, blot on paper towels, and transfer to a large plate. Continue to scoop and cook the remaining meringues. Set aside while you prepare the garnish.
5. Make the spun caramel: Place a clean, dry, heatproof bowl upside-down on a heatproof surface. Lightly grease the bottom of the bowl with nonstick spray. In a small pot, stir together the sugar and 1 tablespoon of water. Dip your fingers in fresh water and wipe down the inside of the pot so no grains of sugar cling to the sides (this will prevent the caramel from crystallizing and becoming sticky). Bring to a boil over medium-high heat. Cook without stirring until the sugar melts and turns dark amber, about 6 minutes. Remove from the heat and gently swirl the pot until the caramel has very slightly thickened, then quickly and carefully, using a spoon or the tines of a whisk, drizzle the caramel over the upturned bowl to create very fine threads. The caramel will set almost instantly; about halfway through drizzling the caramel, transfer the cooled threads to a dry plate and continue with the remaining caramel. (If it becomes too stiff to drizzle, you can re-melt it once or twice over medium-low heat.) 
6. Divide the crème anglaise among six shallow bowls. Top each with two meringues, sprinkle with the praline roses, garnish with a nest of spun caramel, and serve immediately.