Pasta Salad with Fresh Pear, Gorgonzola, and Walnuts

1 1-pound package small shell pasta
1 cup walnut pieces
2 to 3 ripe pears
8 ounces Gorgonzola cheese, crumbled
1 1/2 cups frozen pearl onions, thawed
2 cups arugula leaves, washed
1 Tbsp fresh rosemary, minced
2 small cloves garlic, minced
1/3 cup red wine vinegar
2/3 cup + 2 Tbsp extra virgin olive oil
1 tsp honey
1 tsp crushed red pepper flakes
1 tsp ground mustard
1 tsp ground black pepper
2 tsp salt

Preheat the oven to 325ºF. Place the walnuts on a pan and toast in the oven until lightly browned, for about ten minutes. Bring four quarts of salted water to a boil. Add the pasta and cook until al dente, or for eight to ten minutes. Drain but do not rinse, move to a large bow l and toss with the 2 tablespoons of olive oil. Reserve and allow to cool slightly. Add the walnuts, pears, Gorgonzola, pearl onions and arugula. In a small bowl, mix the remaining ingredients for the dressing, pour over the pasta and lightly toss. Allow the flavors to develop for at least fifteen minutes before serving.