Make crème anglaise: steep vanilla in warm milk 20 minutes. Whisk yolks with allulose. Pour warm milk over yolks. Return to heat, stirring until mixture coats a spoon (82°C). Strain and cool.

Make meringue: whisk whites with a pinch of salt to soft peaks. Add erythritol gradually until stiff and glossy.

Bring a wide pan of water to bare simmer. Using two large spoons, form oval mounds of meringue and slide into water.

Poach 2 minutes per side until just set. Remove with a slotted spoon. Drain on a cloth.

Make caramel: melt allulose in a dry pan until amber. Drizzle from a fork over the islands.

Pool crème anglaise in shallow bowls. Float meringue islands on top.

Serve immediately.