Method:
Preheat oven to 375°F. Spread hazelnuts on a rimmed baking sheet and toast until lightly golden, 10 to 12 minutes. Wrap nuts in a clean dish towel and rub together to remove skins. Set aside until cool enough to handle, and then chop nuts. To make croutons, toss bread cubes with 1 tablespoon olive oil and place on a baking sheet. Toast until golden, 10 to 12 minutes.
Meanwhile, whisk together mustard, vinegar, salt and pepper in a large bowl. Add remaining 2 tablespoons olive oil in a thin steady stream, whisking constantly until combined. Add greens, pears, blue cheese and hazelnuts and toss until evenly coated. Toss in the croutons and serve immediately.