Preheat oven to 350°.
To prepare pecans, combine first 5 ingredients in a small bowl. Rinse pecans with cold water; drain (do not allow pecans to dry). Add pecans to the sugar mixture, and toss well to coat. Arrange pecan mixture on a jelly roll pan coated with cooking spray. Bake at 350° for 10 minutes, stirring occasionally. Coarsely chop pecans. Set aside.
To prepare vinaigrette, combine the shallots and next 7 ingredients (shallots through black pepper) in a small bowl, stirring with a whisk until blended.
To prepare salad, heat a large nonstick skillet coated with cooking spray over medium-high heat. Add prosciutto; sauté 5 minutes or until crisp, and finely chop. Combine spinach, nectarines, and dressing in a large bowl; toss gently to coat. Sprinkle with the pecans and prosciutto.