In a small bowl, beat cream cheese and butter until smooth. Stir in the blue cheese and walnuts. Spread evenly over toasted bread.
Place on a baking sheet. Broil 3-4 in. from the heat for 3-4 minutes or until cheese is bubbly. Core pear and cut into 30 thin slices. Place two pear slices on each crostini. Serve warm.