Carefully halve the pears (try to leave the stalks on 3 of the halves) and scoop out the middles from all of them. Chop the 3 halves that do not have stalks and leave the others cut-side down to drain. Layer the brioche with the chopped pear; arrange the 3 halved pears cut-side down and push them down gently. bring the milk and cream to a simmer with the cardamom, cinnamon and vanilla, and stir in the caster sugar until it dissolves. beat in the eggs and pour the lot into the tin (you can fish out the hard spices or leave them on top while it bakes). Leave to soak for 20 minutes.