Butter a metal cookie sheet and set aside. In non-stick frypan, combine first set of ingredients. Bring to boil over medium-high heat. Stir until sugar is dissolved, about 2 minutes. Mixture will be bubbly and foamy looking (BE CAREFUL THIS IS EXTREMELY HOT!) Add pecan halves and stir while cooking for one and 1/2 minutes. Remove pecans to cookie sheet and spread to separate. Let cool thoroughly. Whisk together dressing ingredients until combined. To assemble salad, toss greens with grapes, nuts and vinaigrette.
Nuts can be done in advance, keep stored in airtight container. Dressing can be made in advance and stored refrigerated.