This dessert can also be baked in an eight-inch square dish; the cooking time will be the same. Serve it warm, at room temperature, or chilled.
Preheat oven to 350 degrees, with rack in center. Butter eight 6-ounce ramekins or custard cups; set aside. Arrange bread in a single layer on two rimmed baking sheets; bake until crisp, tossing once, 15 to 20 minutes. Remove from oven. Reduce oven heat to 300 degrees.
Meanwhile, in a large bowl, whisk together eggs, granulated sugar, milks, cinnamon, vanilla, and salt. Stir in toasted bread; let sit, tossing occasionally, until bread has absorbed liquid, about 5 minutes.
Divide bread mixture evenly among ramekins. Place on a baking sheet; bake until a toothpick inserted in center of a pudding comes out clean, 50 minutes to 1 hour. Let cool. Serve dusted with confectioners' sugar.