For the vanilla sauce: Bring the milk and salt to a simmer
over medium heat in a 2-quart heavy saucepan. Whisk
together the yolks and sugar in a bowl until combined, and then add to the hot milk in a slow stream, whisking. Transfer the custard back to the saucepan
and cook over moderately-low heat, stirring constantly with a wooden spoon, until the custard coats back of a spoon, about 5 minutes. Pour through a fine-mesh sieve
into a bowl and stir in the vanilla. Cover the surface of the custard
with a round of wax paper and chill until cold, at least 1 hour.
For the bread pudding: Preheat the oven to 325 degrees F. In large mixing bowl, toss together the donut slices, dried cherries
and white chocolate
. Set aside. In second large mixing bowl, stir together the sugar, cinnamon and nutmeg
. Measure out 1/4 cup of spiced sugar into a small bowl and set aside.
In a third large mixing bowl, whisk together the eggs, cream, milk
and vanilla. Whisk the eggs
into the large bowl of spiced sugar, and then pour over the bread-chocolate mixture and stir to combine. Pour the batter
into a 9-by-13-by-2-inch baking pan and sprinkle with the reserved 1/4 cup spiced sugar. Scatter the butter cubes over top and bake until golden brown and just set in middle, 50 to 60 minutes.
Serve with the vanilla sauce.