In a large pot, combine red wine, pomegranate juice, and sugar. Stir in cloves, cinnamon, cardamom, allspice, star anise, and orange slices. Heat until it simmers.

Peel the Bosc pears, leaving stems intact. Submerge pears in the poaching liquid, bring to a gentle boil, then reduce heat to low and simmer for 30 minutes.

Check pears for tenderness after 30 minutes. If firm, continue to simmer for an additional 10 minutes.

Remove from heat and cool pears in the poaching liquid. Strain the liquid to yield syrup.

Return strained liquid to boil and reduce until thick and glossy, about 10-15 minutes.

In a bowl, whisk egg yolks, sugar, and vanilla paste until smooth. Scald half-and-half without boiling, then gradually add to egg mixture while whisking continuously.

Return mixture to saucepan and cook over low heat, stirring until thickened, about 5-7 minutes. Strain to remove lumps.

Serve pears with syrup and custard on the side.