Strawberry Spinach Salad with Candied Pecans

Melt butter in a large heavy skillet over medium heat. Add pecans and sugar; stir to combine. Cook over medium heat, stirring constantly until sugar melts around pecans and is caramel-colored. Remove pecans with a slotted spoon and spread in a single layer on a sheet of lightly greased aluminum foil. Cool completely and break up pieces as needed. Remove and discard stems from spinach. Wash spinach and pat dry with paper towels. Tear into bite-size pieces. Combine spinach, celery and strawberries in a large bowl. Pour 1 cup dressing over salad mixture; toss gently. Add reserved candied pecans; toss gently. Serve immediately. Combine first 5 ingredients in container of electric blender; cover and process until smooth. With blender running, gradually add oil in a slow, steady stream through opening in lid. Process until thick and smooth. Transfer dressing mixture to a bowl; stir in poppy seeds. Cover and chill. Store unused portion in refrigerator.