Heat oven to 350 degrees. In a small saucepan over low heat, warm milk, butter, vanilla, sugar and salt. Continue cooking just until butter melts; cool. Meanwhile, butter a 4-to-6-cup baking dish and fill it with cubed bread.

Add eggs to cooled milk mixture and whisk; pour mixture over bread. Bake for 45 minutes, or until custard is set but still a little wobbly and edges of bread have browned. Serve warm or at room temperature.