Heat oven to 350 degrees. Butter four 4-ounce ramekins. In bowl, mix 1/3 cup peanut butter, eggs, sugar, milk, vanilla, and salt. Toss bread cubes in mixture until thoroughly coated.
Divide evenly among prepared dishes. Bake until custard is set in middle and tops are golden, about 35-40 minutes. If tops of bread brown too quickly, cover ramekins loosely with aluminum foil.
In small saucepan over low heat, combine remaining peanut butter and maple syrup until thoroughly warmed. To serve, drizzle ramekins with maple-peanut sauce and garnish with chopped peanuts and powdered sugar.
Substitution: Whole wheat rolls may be used in place of brioche or challah bread.