Pear Bruschetta With Blue Cheese

2 ripe Bartlett or Anjou pears
1 tablespoon fresh lemon juice
1 tablespoon minced fresh Italian flat leaf parsley
2 ounces sharp crumbly blue cheese, like Maytag, Roquefort or Cabrales (about 1/3 cup crumbled)  1 1/2 tablespoons olive oil
Freshly ground black pepper
1 baguette (12-inches), cut into 1/2-inch thick rounds
8 ounces mascarpone cheese 1/4 cup finely chopped walnuts, toasted
Rinse the pears but don't peel them. Cut them into small dice and place in a small bowl. Sprinkle pears with lemon juice and toss. Add the parsley, blue cheese, and oil and toss gently and thoroughly. Season to taste with freshly ground black pepper. Set aside. (The topping can be prepared up to this point up a few hours ahead. Store, covered, in the refrigerator.) Preheat the broiler. Arrange bread slices in a single layer on a baking sheet and toast under the broiler until lightly browned and crisp, 1 to 2 minutes per side. Spread each toast round with a teaspoon of mascarpone. Top with a generous tablespoon of the diced pear mixture, mounding it up high and pressing it firmly. Finish each one with a sprinkling of walnuts and serve.