For the bread pudding: Preheat the oven to 300 degrees F. and place a rack in the center of the oven. Lightly grease four 6-ounce heatproof ramekins with butter. Place the ramekins into a baking dish that is large enough to hold them without touching. Place the bread cubes, apples and raisins in the ramekins, dividing the ingredients evenly.
Using a whisk, beat the eggs, half-and-half, brown sugar, butter, Calvados, vanilla, cinnamon, allspice, nutmeg and a pinch of kosher salt in a bowl until thoroughly combined. Carefully pour the custard over the bread cubes, pressing the bread cubes down so they are covered with the custard. Set aside to allow the bread to absorb the custard, about 15 minutes.
Prepare a water bath: Carefully pour enough hot water into the baking dish so that the water is halfway up the sides of the ramekins. (A water bath is used to provide temperature protection for the egg custard.)
Bake until the tops are golden brown and a toothpick inserted in the center comes out clean, 20 to 30 minutes. Another way to judge whether the puddings are fully baked is to gently press down on the center of each. If any uncooked custard comes up to the top, the pudding needs to be baked a little longer. Remove the bread puddings from the water bath and cool slightly. The puddings can be served warm or slightly chilled.
Meanwhile, make the vanilla bean whipped cream: Put the heavy cream and vanilla bean seeds in a large bowl. Whisk until soft peaks form. Serve immediately with the puddings or refrigerate until ready to use.
The unsweetened whipped cream is meant to temper the sweetness of the bread pudding. Add a tablespoon or two of sugar before beating if you like a sweeter whipped cream.