Combine milk, zest, cloves, cinnamon and vanilla bean and seeds in a saucepan. Bring to the boil over medium heat and cook until reduced to 750ml (12-15 minutes). Remove from heat, add sugar and stir to dissolve. Cool.
Preheat oven to 180C. Grease six 1-cup capacity heatproof ramekins with butter. Stir milk mixture and pour through a fine seive into a mixing bowl, discarding solids. Whisk in the eggs and yolks then pour into ramekins. Cover ramekins with foil, place in a tea towel-lined baking dish, making sure they are not touching each other. Fill baking dish with boiling water three-quarters up the sides of the ramekins and bake until a knife inserted withdraws clean (40-50 minutes). Cool for 15 minutes, remove from baking dish and refrigerate until chilled (1-2 hours).
Meanwhile for the saba, boil the mosto in a small saucepan over high heat until reduced by half (20-30 minutes). Cool.
To serve, invert puddings, pour a little saba over, garnish with a few grapes and serve immediately.
Note Mosto is the Italian for fresh grape juice. Anna Maria uses Robinvale red grape juice.